STUDY OF THE VERTICAL AUTOROTATION OF A SINGLEWINGED SAMARA

1. Autorotation of a single-winged samara is a highly nonlinear phenomenon that represents a delicate equilibrium between gravity, inertia and aerodynamic effects. Therefore, in order to analyse this phenomenon, an accurate detailed model is necessary. Such a model has not been presented in the past. Recently the authors derived a detailed model which is briefly described in the paper. 2. The aerodynamic contributions present the most complicated part of the phenomenon. These contributions are treated using the blade-element/momentuin method, with certain improvements and additions. These improvements are necessary due to inherent differences between samara wings and other rotary wing systems (aircraft propellers, helicopter rotors, etc.). 3. The cross-sectional aerodynamics of the samara is characterized by relatively small Reynolds numbers, high angles of attack and rough surfaces. While these characteristics are different from other rotary wings, they are typical of the wing cross-sections of insects and birds. Therefore the lift and drag coefficients, which are necessary for the analysis, are obtained using available data for insect and bird wings. 4. The results of the theoretical model are compared with experimental results of tlvo kinds. The first kind includes results for a samara of an Acer platanoides that were reported in the literature. In addition, a special experimental model of a samiira was built and tested. This model offers a simple way of varying the configuration in order to study (experimentally) the effect of different geometric parameters on the autorotation. 5. In the light of the uncertainty in the aerodynamic coefficients, it can be concluded that there is quite a good agreement between the theoretical and experimental results. Thus, after LTalidation, the theoretical model is used for a parametric study to find the influence of different parameters on the autorotation. The important results of this study are outlined below. 6. The spanwise flolv component and the tangential component of the induced velocity have a very small influence and thus can be neglected. 7. It is important to include in the analysis the effects of the axial induced velocity, the tip effect, and the drag of the root region. 8. Since chordwise variations of the centre of pressure location, as a function of the angle of attack, were seen in the past (based on over simplified analyses) as the mechanism which is responsible for the samara stability, this effect is also added to the model. While the influence of this effect on the pitch angle is large and small on the sinking rate, it results in an increase in the deviation between the theoretical and experimental results. 9. Autorotation is sensitive to the cross-sectional aerodynamic coefficients. This sensitivity is critical since the available data on these coefficients is, to say the least, unsatisfactory and require significant improvement.     

THE TERMINAL VELOCITY AND DISPERSAL OF SPINNING SAMARAS

Strobe photographs were taken of over 200 spinning samaras from seven species of trees. These were used to measure the rate of descent, angular velocity, orientation, and other parameters of the samaras as they fell. These data were then used to compare the aerodynamic behavior of samaras, helicopters, and theoretical ideal rotors. Plotting morphological data for each samara against its rate of descent showed that this rate was highly correlated with the square root of the samara's wing loading (samara weight divided by wing-surface area). This plot demonstrated the existence of two distinct groups of samaras, distinguished by their morphology, spinning motion, and rate of descent. These results are of greatest use in characterizing local dispersal patterns.     

Diversity and evolution of samara in angiosperm

翅果能够依靠风力进行传播, 可能是被子植物快速散布和物种分化的一个重要因素。狭义的翅果是指果皮延伸成翅且不开裂的干果; 广义的翅果则包括果皮、花被片或苞片形成果翅的所有果实。根据果翅形态及其生长方式的不同, 广义的翅果可分为单侧翅果、周位翅果(圆翅果与蝶翅果)、棱翅果、披针翅果、翼状萼翅果、叶状苞翅果6种类型, 其空中运动方式有自旋式(单侧翅果、翼状萼翅果)、波浪式(周位翅果、叶状苞翅果)、翻滚自旋式(周位翅果)、直升机式(披针翅果、翼状萼翅果)和滚筒式(棱翅果)。棱翅果与圆翅果在被子植物基部类群樟目就有发生, 并同时出现在单子叶植物和双子叶植物中, 可能是最早出现的翅果类型。翅果的演化过程呈现出果翅数量增加、果翅偏向单侧和果翅负荷(果实质量与果翅面积之比)降低的趋势, 以利于适应较小的风并增加传播距离。果翅除了促进果实与种子的风力传播外, 还具有物理防御、调节种子萌发和促进二次传播等作用。泛热带分布的金虎尾科有着极其丰富的翅果类型, 与其多次跨洋长距离扩散密切相关, 可以作为研究翅果适应与演化的一个模式类群。结合生态和演化-发育生物学方法, 研究不同类型翅果在适应风力传播方面的差异、萼片或苞片发育成翅的分子与遗传机制、翅果不同类型的演化历史及其对被子植物物种多样性的影响等是今后值得探讨的重要问题。     

被子植物翅果的多样性及演化

翅果能够依靠风力进行传播, 可能是被子植物快速散布和物种分化的一个重要因素。狭义的翅果是指果皮延伸成翅且不开裂的干果; 广义的翅果则包括果皮、花被片或苞片形成果翅的所有果实。根据果翅形态及其生长方式的不同, 广义的翅果可分为单侧翅果、周位翅果(圆翅果与蝶翅果)、棱翅果、披针翅果、翼状萼翅果、叶状苞翅果6种类型, 其空中运动方式有自旋式(单侧翅果、翼状萼翅果)、波浪式(周位翅果、叶状苞翅果)、翻滚自旋式(周位翅果)、直升机式(披针翅果、翼状萼翅果)和滚筒式(棱翅果)。棱翅果与圆翅果在被子植物基部类群樟目就有发生, 并同时出现在单子叶植物和双子叶植物中, 可能是最早出现的翅果类型。翅果的演化过程呈现出果翅数量增加、果翅偏向单侧和果翅负荷(果实质量与果翅面积之比)降低的趋势, 以利于适应较小的风并增加传播距离。果翅除了促进果实与种子的风力传播外, 还具有物理防御、调节种子萌发和促进二次传播等作用。泛热带分布的金虎尾科有着极其丰富的翅果类型, 与其多次跨洋长距离扩散密切相关, 可以作为研究翅果适应与演化的一个模式类群。结合生态和演化-发育生物学方法, 研究不同类型翅果在适应风力传播方面的差异、萼片或苞片发育成翅的分子与遗传机制、翅果不同类型的演化历史及其对被子植物物种多样性的影响等是今后值得探讨的重要问题。     

SEED DYNAMICS OF ABIES BALSAMEA AND ACER SACCHARUM IN A DECIDUOUS FOREST OF NORTHEASTERN NORTH AMERICA

We studied the seed dynamics of Abies balsamea and Acer saccharum in a sugar maple-yellow birch forest of Québec, Canada. Seed rain was censused every week from spring to autumn in 1988 and 1989. The soil seed bank was sampled four times during the 1988 growing season. Abies seed rain varied significantly between 1988 and 1989. A total of 92.5 ± 7.0 seeds nr^-2 (mean ± 1 SE) were produced in 1988; 1989 seed production was null. Seed viability in 1988 averaged 31.5%. Dispersal during the winter period accounted for ca. 22% of the annual seed crop. The spatial dispersion pattern of the seed rain was contagious for the autumn period, but was not significantly different from random for the winter period. There was only a weak relationship in the spatial distribution of the seed rain between the autumn and winter periods. Abies did not maintain a persistent seed bank on the site; viable seeds were present on the soil only after seed dispersal had started. Postdispersal seed mortality was relatively high, ca. 70%. Acer seed rain started soon after the flowering period, but consisted at that time only of aborted, underdeveloped samaras. Viable seeds were disseminated from September through early winter. Dispersal during the autumn accounted for ca. 98% of the annual seed crop. There were significant differences between seed rain abundance of 1988 and that of 1989 (118.1 ± 9.5 samaras m^-2 and 158.9 ± 16.3 samaras m^-2 in 1988 and in 1989, respectively). Seed viability also varied significantly between the 2 years, i.e., 19% in 1988 and 5% in 1989. For both 1988 and 1989, samaras were contagiously dispersed over the site. There was a significant positive relationship between the spatial distribution of the seed rain in 1988 and that in 1989. Seed rain abundance was high mainly in the proximity of mature Acer trees. As for Abies, Acer did not maintain a persistent seed bank in the soil; viable seeds were present only in the autumn seed bank sampling, after seed fall had started. Postdispersal seed mortality was relatively low, i.e., 20%. Abies and Acer are quite similar in their regenerative traits, and these contrast sharply with those of Betula alleghaniensis, a regular member of this forest community. Differences in regenerative traits may contribute to the coexistence of these tree species considering the gap regime of the system studied.     

Fossil Ptelea samaras (Rutaceae) in North America

Fossil samaras referred to the extant rutaceous genus Ptelea L. comprise an artificial collection of five distinct taxa with convergent fruit morphologies. Critical reexamination of these fossils revealed that only one of the five samara types can be referred to Ptelea. Two of the forms can be assigned without reservation to Tiliaceae (Pteleaecarpum = Craigia) or Caprifoliaceae (“Ptelea” cassioides [part], “Ptelea” miocenica [part]). Taxonomic affinities of the two remaining fruit types (“Ptelea“ eocenica, “Ptelea“ cassioides [part]) are undetermined. Genuine fossil Ptelea samaras are restricted to Miocene floras in the western United States, including the Hog Creek (Weiser) and Succor Creek floras near the Oregon–Idaho border and the Stinking Water flora of east-central Oregon. These samaras bear the names P. miocenica Berry and P. enervosa H. V. Smith. The holotype of P. miocenica is a caprifoliaceous infructescence similar to that of Dipelta Maximowicz, so P. enervosa, previously considered a synonym of P. miocenica, is the valid combination for fossil Ptelea samaras. P. enervosa samaras are the oldest reliably determined fossil Ptelea fruits. These samaras indicate that the Toddalieae-Pteleinae lineage of subfamily Toddalioideae has been present in North America since the Miocene, rather than the Eocene as suggested by previously misidentified specimens.     

长白山9种槭树的翅果扩散及种子萌发研究

翅果的风媒传播是槭属植物的主要扩散方式之一,且与种子萌发有着密切关联,但具体机理一直还并不明确。以分布于长白山的9种槭树为对象,探讨翅果的形态特征,测定它们在空气中的垂直沉降速度、不同风速下的水平扩散距离以及在扩散距离上的种子萌发率,进而比较并分析翅果的形态性状与沉降速度、水平扩散距离的相关性以及萌发率在不同扩散距离上的差异性。结果表明：(1) 9种槭树的翅果长、宽和面积与沉降速度、水平扩散距离均呈负相关;尽管如此,翅果形态并不是风传播物种的最佳分类指标,而翅载力能较好地反应物种的风传播能力;(2)翅果垂直沉降速度和水平扩散距离间存在显著负相关,表明沉降速度越小,翅果在空气中停留的时间越长,水平方向上扩散距离越远,且强风有助于提高翅果的扩散能力;(3)沉降速度最慢的花楷槭在不同风速下的水平扩散距离均最远,而沉降速度最快的拧筋槭水平扩散距离最短;(4)种子萌发率随扩散距离的增加呈下降趋势。上述结果不仅为深入理解翅果的风力传播机制以及种子萌发对水平扩散距离的响应机制提供科学依据,还可为种群实生更新方面的理论研究提供参考。     

From falling to flying: the path to powered flight of a robotic samara nano air vehicle

This paper details the development of a nano-scale (>15 cm) robotic samara, or winged seed. The design of prototypes inspired by naturally occurring geometries is presented along with a detailed experimental process which elucidates similarities between mechanical and robotic samara flight dynamics. The helical trajectories of a samara in flight were observed to differ in-flight path and descent velocity. The body roll and pitch angular rates for the differing trajectories were observed to be coupled to variations in wing pitch, and thus provide a means of control. Inspired by the flight modalities of the bio-inspired samaras, a robotic device has been created that mimics the autorotative capability of the samara, whilst providing the ability to hover, climb and translate. A high-speed camera-based motion capture system is used to observe the flight dynamics of the mechanical and robotic samara. Similarities in the flight dynamics are compared and discussed as it relates to the design of the robotic samara.     

The effect of samara wing presence on predation of Acer pseudoplatanus (Sapindaceae) seeds on the ground

The key selective pressure shaping the morphology of samaras is seen as enhancing primary wind-borne dispersal from the parent plant to the ground. However, the consequences of the samara wing of primarily wind-dispersed tree species for post-dispersal processes has not been well studied. We explored whether the presence of this wing in Acer pseudoplatanus either deters or promotes predation after dispersal, either by increasing the time and energy required to predate the seed or by increasing the seed's visibility to predators. We found that wing-removed fruits were preferred, suggesting that the presence of samaras makes seed handling more expensive for granivores. Further, we found that fewer seeds were consumed from treatments that contained the most winged seeds, thus there was no evidence of the samaras making seed finding easier for granivores. We conclude that the presence of the wing may offer an anti-predatory benefit as well as aiding primary dispersal.     

Seed size and dispersal potential of Acer rubrum (Aceraceae) samaras produced by populations in early and late successional environments

In order to determine if red maple dispersal potential or seed size change during secondary succession, samaras were collected from five populations located in early successional environments and five populations located in late successional environments. Wing loading ratios (samara mass—mg/samara area—cm²), which are inversely proportional to dispersal ability, were computed for all samaras, and seeds were excised from each samara and weighed. Samaras from the early successional red maples showed slightly but significantly lower wing loading ratios than those from the late successional environments. This result corresponds with the conclusions reached by several theoretical investigations of seed dispersal evolution that predict that recently founded populations will show greater dispersal abilities than more established populations. The earlier successional populations had slightly heavier seeds than the later successional populations, which suggests that the changes in community composition and dynamics that occur during this successional sequence do not select for heavier seeds in older red maple populations. Coefficients of variation for wing loading and seed size showed no consistent trends with successional stage, which indicates that variation in these characters does not decrease as succession proceeds.     

First fossil evidence of samaras of Ventilago Gaertn. (Rhamnaceae) from India and its implications

The Ventilago Gaertn. (Rhamnaceae) is widely distributed in pantropical areas of Africa, Asia, and Australia. However, fossil records of this taxon are sparse, which limits understanding of the evolution and biogeographic history of the genus. In the present study, we report and describe two new fossil species of Ventilago, V. siwalika sp. nov. from the Miocene sediments of Himachal Pradesh, western Himalaya, and V. pliocenica sp. nov. from the Pliocene sediments of Jharkhand, eastern India based on single-winged samaras. Ventilago pliocenica is characterized by a prominent midvein, obtuse to sub-round apex with mucronate tip, longitudinal secondary veins extending the full length of the fruit, and reticulate nature of higher-order veins, the presence of equatorial rim, the hypanthium, and short pedicel. On the other hand, V. siwalika is characterized by a prominent midvein, obtuse to sub-round apex with mucronate tip, longitudinal secondary veins extending the full length of the fruit, and reticulate nature of higher-order veins. Our discovery represents the first unambiguous fossil record of single-winged samara of Ventilago from India and provides valuable insights into the evolution of this genus. In this paper, we also review its biogeographic history and add new information to understand its hypothetical migration route. Present and earlier records of Ventilago also suggest that this genus was a common forest element during Neogene (Miocene time) in Asia.     

Gone with the wind and the stream: Dispersal in the invasive species Ailanthus altissima

Dispersal is a key process in plant invasions and is strongly related to diaspore morphology. Often, dispersal comprises more than one step, and morphologies adapted to a primary dispersal mechanism can aid or detract from a secondary one. The aim of this work was to assess the relationship between primary wind dispersal and secondary water dispersal in Ailanthus altissima, an invasive tree species. Wind and water dispersal potential and their association with the morphological characteristics of samaras were assessed under controlled conditions to ensure the repeatability of the measurements. We found a direct positive relationship between primary wind and secondary water dispersal in A. altissima. The main morphological characteristics of the samara that affected the success of the two types of dispersal were side perimeter and mass. However, a possibility of dispersal specialisation exists, as one morphological characteristic (samara width) affects wind dispersal negatively but water dispersal positively, and dispersal potential and samara morphology have been shown to differ across individuals.     

Morphological,structural and physiological differences in heteromorphic leaves of Euphrates poplar during development stages and at crown scales

• Euphrates poplar (Populus euphratica Oliv.) has heteromorphic leaves including strip, lanceolate, ovate, and broad‐ovate leaves from base to top in the mature canopy.
• To clarify how diameter at breast height (DBH) and tree height affect the functional characteristics of all kinds of heteromorphic leaves, we measured the morphological anatomical structure and physiological indices of five crown heteromorphic leaves of P. euphratica at 2, 4, 6, 8, 10, and 12 m from the same site. We also analysed the relationships between morphological structures and physiological characteristics of heteromorphic leaves and DBH and the height of heteromorphic leaves.
• The results showed that the number of abnormalities regarding blade width, leaf area, leaf thickness, leaf mass per area, cuticle layer thickness, palisade tissue thickness, and palisade tissue/sponge tissue ratio increased with size order and sampling height gradient. Net photosynthetic rate, transpiration rate, stomatal conductance, instantaneous water use efficiency, stable delta carbon isotope ratio, proline and malondialdehyde (MDA) content increased with DBH and sampling height. By contrast, blade length, leaf shape index, and intercellular CO2 concentration decreased with the increase in path order and sampling height gradient. Although MDA content and leaf sponge thickness were not correlated with DBH or sampling height, other morphological structure and physiological parameters were significantly correlated with these variables. In addition, correlations were found among leaf morphology, anatomical structure, and physiological index parameters indicating that they changed with path order and tree height gradient.
• The differences in the morphology, anatomic structure and physiological characteristics of the heteromorphic leaves ofP. euphratica are related to ontogenesis stage and coronal position.

     

Intraspecific variation in samara morphology and flight behavior in acer saccharinum (Aceraceae)

We studied intraspecific variation in samara morphology and flight behavior within and among parent trees of Acer saccharinum (silver maple), with a particular focus on the effect of samara shape. Samara mass, area, wing loading, and descent rate from a 4.5-m indoor balcony were measured for 50 undamaged mature samaras from each of six parents. We found significant differences among parental types for all morphological variables and descent rate. These differences yielded a 50% range in mean dispersal potential among the six parents. There was a strong linear correlation between descent rate and square root of wing loading when mean values were plotted for each of the six parental types. But there was considerable within-parent variation for all measured variables, including substantial nonallometric variation in wing loading caused in part by poor correlations between wing area and fruit weight. Parents also differed widely in the relationship between square root of wing loading and descent rate (linear r² = 0.150-0.788), with one parental type showing no significant relationship. Fruits from the same parent with similar values of the square root of wing loading showed as much as a 75-100% difference in descent rate. The usefulness of mass : area indices such as wing loading is limited by its exclusion of aerodynamically important factors such as mass distribution and wing shape, which in our case caused the six parents to behave aerodynamically almost as if they were six separate species.     

CYTOPLASMIC ORGANIZATION AND RHYTHMIC STREAMING IN GROWING BLADES OF CAULERPA PROLIFERA

Light- and electron-microscopic studies of the growing blades and their meristematic tips in Caulerpa prolifera have been correlated with time-lapse photographic studies. The growing blade may be divided into three zones based on the level of maturation. A “meristemplasm” is present at the tip of the growing blade and at sites of wounding. The cytoplasm of these growing regions has an abundant endoplasmic reticulum, Golgi bodies, amyloplasts, and nuclei, but lacks chloroplasts and a central vacuole. An intermediate zone lies between the white meristemplasm and the green, mature basal zone. The basal zone contains a parietal cytoplasm with organelles typical of the Chlorophyta and a dominant central vacuole. Two distinct systems of cytoplasmic streams occur in the basal zone and both contain packets of microtubules orientated parallel to the axis of the streams. As the blade matures and growth ceases, the dominant central vacuole forms up to the tip. In developing blades the tips become white in the absence of light as a result of basipetal movement of the chloroplasts. In plants kept on a 12-hr L: 12-hr D cycle, blade growth and chloroplast migration at the blade tip are rhythmic, and the peak occurs about 2-4 hr after initiation of the dark phase. Experiments are reported using continuous light or darkness after three 24-hr periods of 12-hr L: 12-hr D phasing.     

Chemical Composition and Phytotoxic Effects of Essential Oils Obtained from Ailanthus altissima (Mill.) Swingle Cultivated in Tunisia

Ailanthus altissima Mill. Swingle (Simaroubaceae), also known as tree of heaven, is used in the Chinese traditional medicine as a bitter aromatic drug for the treatment of colds and gastric diseases. In Tunisia, Ailanthus altissima is an exotic tree, which was introduced many years ago and used particularly as a street ornamental tree. Here, the essential oils of different plant parts of this tree, viz., roots, stems, leaves, flowers, and samaras (ripe fruits), were obtained by hydrodistillation. In total, 69 compounds, representing 91.0–97.2% of the whole oil composition, were identified in these oils by GC‐FID and GC/MS analyses. The root essential oil was clearly distinguishable for its high content in aldehydes (hexadecanal ( 1 ); 22.6%), while those obtained from flowers and leaves were dominated by oxygenated sesquiterpenes (74.8 and 42.1%, resp.), with caryophyllene oxide ( 4 ) as the major component (42.5 and 22.7%, resp.). The samara oil was rich in the apocarotenoid derivative hexahydrofarnesyl acetone ( 6 ; 58.0%), and the oil obtained from stems was characterized by sesquiterpene hydrocarbons (54.1%), mainly β‐caryophyllene (18.9%). Principal component and hierarchical cluster analyses separated the five essential oils into four groups, each characterized by the major oil constituents. Contact tests showed that the germination of lettuce seeds was totally inhibited by all the essential oils except of the samara oil at a dose of 1 mg/ml. The flower oil also showed a significant phytotoxic effect against lettuce germination at 0.04 and 0.4 mg/ml (?55.0±3.5 and ?85.0±0.7%, resp.). Moreover, the root and shoot elongation was even more affected by the oils than germination. The inhibitory effect of the shoot and root elongation varied from ?9.8 to ?100% and from ?38.6 to ?100%, respectively. Total inhibition of the elongation (?100%) at 1 mg/ml was detected for all the oils, with the exception of the samara oil (?74.7 and ?75.1% for roots and shoots, resp.).     

Design of the predatory legs of water bugs (Hemiptera: Nepidae,Naucoridae, Notonectidae,Gerridae)

Functional comparative morphology of predatory legs in five species of water bugs (Ilyocoris cimicoides, Nepa cinerea, Ranatra linearis, Notonecta glauca, and Gerris lacustris) has been investigatd adn the following peculiarities of leg design were revealed.

• 1 Subcoxal articulation may be monoaxial (G. lacustris, N. glauca), or, in contrast to walking leg type, biaxial (N. cinerea, R. linearis, I. cimicoides); the first axis is oriented along the coxa (torsion axis), the second one is perpendicular to the first (non-torsion axis).
• 2 In contrast to walking leg type, which is characterized by cross suspension of the axis of coxal rotation in thoracal skeleton, this axis in G. lacustris is placed vertically. Non-torsion coxal axis in R. linearis is oriented strongly transversal. This axis directs the leg strike forward.
• 3 Legs in the majority of species are planar: Torsion axes of the coxa, femur, and tibia are placed in the same plane. Axes of rotation of consequent joints in I. cimicoides are reciprocally sloped. Therefore, the end of the leg outlines the spiral trajectory, when all angles of joints are opening (closing). This is an adaptation for clinging to the stems of water plants.
• 4 Passive adduction of the femur in the trochanter-femoral joint in N. glauca allows it to go around protuberances of the body wall, when the leg is sliding along them; recurrent femur movement during releasing from the obstacele is active due to the rt.fe muscle.
• 5 Only R. linearis has predatory legs, which permit the high-speed pursuit of potential prey; other species realize this function using the swimming legs, whereas the forelegs are used for the manipulation movements.
• 6 Muscle arrangement in the prothorax of different species reflects both leg construction and constructional constraints of body design. Powerful flexor muscles (co1, co2, co3, co5, fl.ti, et.ti in R. linearis; fl.ta, fl.ti in N. glauca; fl.ti in I. cimicoides) have long tendons and short muscle bundles, which originate on the leg wall. As a result, the powerful force is developed along the muscle tendon.
• 7 Some features of the predatory leg are common for the species studies: elongation of coxae, thickening of femora, and increase of the degree of junction of tibia and tarsus. The muscles, which move the distal segment of the leg, are reinforced and the sclerite of the fl.ti tendon is enlarged. The joint angle of the distal segment is increased to 120°. © 1995 Wiley-Liss, Inc.

     

The nutritional quality of phloem sap utilized by natural aphid populations

Abstract.

• 1 The amino acid content of phloem exudates from leaves and of aphid honeydew were adopted as indices of the nutritional quality of phloem sap for aphids. Four plant species and associated leaf-dwelling aphids were investigated: the sycamore Acer pseudoplanatus and sycamore aphid Drepanosiphum platanoides; Prunus domestica (victoria plum) and the mealy plum aphid Hyalopterus pruni; and the spindle tree Euonymus europaeus and broad-bean Vicia faba, both hosts of the black bean aphid Aphis fabae.
• 2 The concentration of amino acids in the phloem exudates varied with: (a) plant species (greater in the herb Vicia than in the tree species), (b) season (greater in the autumn than summer for Acer and Euonymus), and (c) position (greater in flush leaves than mature leaves of Prunus).
• 3 For Acer and Prunus and their aphids, the concentration of amino acids in phloem exudates was significantly correlated with the amino acid content of the aphid honeydew.
• 4 The amino acids in all exudates and honeydew were dominated by non-essential amino acids (glutamic acid, glutamine, asparagine or serine, varying with season and between plant species). The sole major discrepancy between the amino acid profiles of exudates and honeydew was the production of asparagine-rich honeydew by aphids feeding on leaves, whose exudates were dominated by glutamic acid; this applied to both H.pruni on mature Prunus leaves and Drepanosiphum platanoides on summer-leaves of Acer.
• 5 It is suggested that EDTA-exudation may be a useful technique to study nutritional correlates of aphid life cycles, e.g. the time of migration between primary and secondary plant hosts.

     

THE FLORAL ANATOMY OF DIPTERONIA

Hall , Benedict A. (State U. of New York, Cortland.) The floral anatcmy of Dipteronia. Amer. Jour. Bot. 48(10): 918–924. Illus. 1961.—The floral morphology of Dipteronia sinensis closely resembles that of such species of Acer as A. pseudosieboldianum. Both these species share the following characters: (1) complete flowers; (2) functional unisexuality of staminate flowers, resulting from abortion of the pistil; (3) andromonoecious condition, the same tree bearing both perfect and functionally staminate flowers; (4) nectariferous disc, extrastaminal in position. The vascular anatomy of the 2 species, described in detail in this paper, differs only in minor ways, having similar traces supplying, respectively, perianth, androecium and gynoecium. The greatest difference between the 2 genera lies in the form of the mature fruit, which in Dipteronia has the wings of the samaras completely surrounding the seeds; yet in both genera the vascular skeleton of the fruit is essentially the same. There is a similar cohesion of the vascular traces of sepals and petals in both these species. Differences between these and certain other species of Acer such as A. negundo and A. carpinifolium, herein described, greatly exceed those between A. pseudosieboldianum and Dipteronia. The flowers of A. negundo, for example, have undergone extreme reduction from the presumed ancestral type, having no petals or disc and lacking either stamens or carpels. These facts support the inclusion of Dipteronia in the Aceraceae, but make questionable its status as a genus separate from Acer.