ANATOMY AND AFFINITIES OF PENTHORUM

The genus Penthorum L. consists of two species of perennial herbs, P. sedoides of eastern North America and P. chinense of eastern Asia. Penthorum has long been considered intermediate between Crassulaceae and Saxifragaceae. An anatomical study of both species was undertaken to contribute to a better understanding of the relationships of these plants. Prominent anatomical features of Penthorum include: an aerenchymatous cortex and closely-spaced collateral vascular bundles of stems; one-trace unilacunar nodes; brochidodromous venation, rosoid teeth bearing hydathodes, and anomocytic stomata of leaves; angular vessel elements with many-barred scalariform perforation plates and alternate to scattered intervascular pits; thin-walled non-septate fiber-tracheids; abundant homocellular erect uniseriate and biseriate rays; and absence of axial xylem parenchyma. In general, Penthorum possesses neither the morphological nor the anatomical synapomorphies which define Crassulaceae, and features shared with Saxifragaceae are largely symplesiomorphous. Thus Penthorum is probably best classified in the monogeneric Penthoraceae.     

LEAF HAIRS IN ENCELIA (ASTERACEAE)

Four different kinds of leaf hairs occur in Encelia species. These are unicellular-based and multicellular-based uniseriate hairs, moniliform hairs, and biseriate glandular hairs. The unicellular-based uniseriate hairs appear responsible for increased leaf spectral reflectance by species within the genus. In particular, it appears that elongation of the distal cell of the uniseriate hair is necessary for increased leaf reflectance.     

“Out-of-India” dispersal for Adina (tribe Naucleeae; family Rubiaceae): evidence from the early Eocene fossil record from India

This study reports the oldest fossil record of the genus Adina, A. vastanenesis n. sp., from the early Eocene of Vastan lignite mine (Cambay Shale Formation), Surat district, Gujarat. This fossil wood is characterized by diffuse porous wood, predominantly solitary tylosed vessels, simple perforations, scanty paratracheal to diffuse to sometimes diffuse in aggregate axial parenchyma, predominantly uniseriate to occasionally biseriate rays, and non septate fibres with bordered pits and shows its best resemblance with the modern species, Adina multifolia Haviland, belonging to the tribe Naucleeae (subfamily Cinchonoideae) of the family Rubiaceae. The present discovery becomes the first fossil record of the wood of Adina, which provides an insight about the Gondwanan origin either for the genus Adina or the tribe Naucleeae and its further dispersal to Southeast Asia.     

CALLIXYLON FROM THE UPPER DEVONIAN OF NORTHWESTERN ALBERTA

Campbell, J. D. (Res. Council Alberta, Edmonton.) Callixylon from the Upper Devonian of northwestern Alberta. Amer. Jour. Bot. 50(7): 648–652. Illus. 1963.—An oil-well core from the “Granite Wash” of probable early Late Devonian age (Wood bend equivalent) in the Peace River region of northwestern Alberta yielded a thin pyritized chip of coniferoid wood. The pith is not represented, but the secondary tracheid pitting, exhibiting radially aligned clusters of 5–10 araucarioid pits, indicates that the specimen is referable to the wood-type usually called Callixylon, now believed to be the axis of the leaf-genus Archaeopleris. In its low and regularly uniseriate or rarely biseriate rays, with no apparent ray tracheids, the specimen may resemble the species Callixylon trifdievi Zalessky (1909) from the Upper Devonian of Russia, and thus lend some small support to the postulation of a Late Devonian land connection between northwestern North America and Europe.     

Comparative Anatomy of Secondary Phloem in Celastraceae

A comparative anatomical study on the secondary phloem of 5-genera, 10 species in Celastraceae was carried out. Based on the phloem structure characters, 3 phloem types were observed. In type Ⅰ , as seen in 5 species of Euonymus, the sieve-tube elements have more inclined end walls and numerous sieve areas (compound sieve plates), phloem rays are almost uniseriate. Type Ⅱ is seen in Celastrus and Tripterygium. It has relatively short sievetube elements, slight inclined end wall and sparse number of sieve areas: the phloem fiber is not lignified and ray is multiseriate. Type Ⅲ is observed in Dipentodon and Perrottetia, the sieve-tube elements are with simple sieve plate, the end wall is almost transverse, there are sclereid and fiber groups in the nonfounctional phloem, and phloem rays are uniseriate or biseriate.     

Illicioxylon, an Element of Gondwanan Polar Forests? Late Cretaceous and Early Tertiary Woods of Antarctica

The Late Cretaceous and early Tertiary sediments from the northernPeninsula region of Antarctica yield a rich assemblage of fossilwood with well preserved anatomy. Wood specimens of a previouslyrecognized morphotype are described. The woods are characterizedby diffuse porous wood, mainly solitary vessels with long scalariformperforation plates, scalariform and opposite vessel-ray pitting,generally uniseriate and biseriate heterogeneous rays, and tracheidswith obvious uniseriate, circulate, bordered pits. These fossilspecimens show greatest anatomical similarity to the organ genusIllicioxylon Gottwald and extant members of the Illiciaceae.The occurrence of illiciaceous-like wood in Gondwana suggeststhat the distribution of this family may have been more widespreadin the geological past and that a relatively warm temperateclimate prevailed over the northern Peninsula region of Antarcticaduring the Late Cretaceous and early Cenozoic. Copyright 2000Annals of Botany Company Fossil, wood, Illiciaceae, Illicioxylon, Illicium, Cretaceous, Tertiary, Gondwana, Antarctica     

ANATOMICALLY PRESERVED GLOSSOPTERIS STEMS WITH ATTACHED LEAVES FROM THE CENTRAL TRANSANTARCTIC MOUNTAINS,ANTARCTICA

Stems and buds of Glossopteris skaarensis Pigg and buds of G. schopfii Pigg from the Permian Skaar Ridge locality in the central Transantarctic Mountains, Antarctica demonstrate the first anatomically preserved glossopterids known with stem/leaf attachment. Stems of G. skaarensis are 1–12 mm in diameter ( = 3.1 mm) with a broad pith, poorly defined primary xylem, and a zone of secondary xylem up to 6 mm thick. Pycnoxylic wood conforming to Araucarioxylon Kraus is composed of tracheids with uni- to biseriate oval to hexagonal bordered pits on radial walls, uniseriate rays one to a few cells high, and cupressoid to taxodioid cross-field pitting. Stems have a narrow zone of secondary phloem, aerenchymatous cortex with scattered sclereids, and sometimes a narrow periderm. Two wedge-shaped leaf traces each bifurcate to form four strands in the base of each petiole. Small axillary branches are vascularized by double branch traces that fuse at the margin of the main axis. Buds of G. skaarensis have leaves with narrow lateral laminae and a thickened midrib containing a wide lacuna, delicate vascular strands, and a prominent hypodermis. In contrast, buds of G. schopfii have uniformly thick leaves with prominent, circular vascular bundle sheaths. These anatomical details are used to reconstruct individual types of glossopterid plants, providing new information toward understanding the ecology and evolution of this important group of Permian seed plants.     

Lewinskya transcaucasica (Orthotrichaceae,Bryopsida) sp. nov. A contribution to the bryophyte flora of Georgia

A new orthotrichaceous species, Lewinskya transcaucasica Eckstein, Garilleti & F.Lara, is described, based on several samples collected in the Georgian territories of Greater Caucasus and Lesser Caucasus. The species is best differentiated by its sporophytic characteristics. Its capsules are long ovoid to cup-shaped and smooth and show no differentiation of the longitudinal bands of the exothecial cells. The capsules vary from emerging fully from the perichaetial leaves to having a shortly exserted position. The peristome is double, with an exostome of eight pairs of orange to crimson teeth whose tips are variably cancellated and fenestrated and recurved when dry, and an endostome of eight segments that occasionally alternate with reduced intermediate segments. All of these segments are yellowish to pale orange, mainly linear, uniseriate or partially biseriate, and strongly ornamented on the inner side. The new moss is illustrated and compared with similar taxa around the world.     

Developmental anatomy of vascular cambium and periderm ofBotrypus virginianus and its bearing on the systematic position of ophioglossaceae

The developmental anatomy of the vascular cambium and periderm ofBotrypus virginianus was studied, and its bearing on the systematic position of Ophioglossacease is discussed. The cambial zone including cambium is initiated in a procambial ring of the stem before primary vascular tissue is well differentiated. The presumed cambium is composed of fusiform and ray initials. The cambium is extremely unequally bifacial, producing secondary xylem centripetally, and quite a small number of parenchymatous cells but no secondary phloem centrifugally. The cambial activity persists long, although it is very low in the mature part of the stem. It seems that the circumferential increase of the cambium is accommodated by an increase in the number of cambial initials. Secondary xylem is nonstoried and composed of tracheids with circular-bordered pits with evenly thick pit membranes, and uniseriate or partly biseriate radial rays. It makes up the bulk of the stem xylem. Periderm is formed almost entirely around the stem, simultaneous with its increment due to the secondary xylem. The combination of these anatomical features of secondary tissue supports the idea that Ophioglossaceae are living progymnosperms.     

LEAF TRICHOMES OF SOME PARTHENIUM SPECIES

Guayule (Parthenium argentatum), a native shrub of the Chihuahuan desert, contains rubber. Guayule has been crossed with other Parthenium species in an attempt to improve its agronomic characteristics. The resulting hybrids show intermediate morphologies. Each Parthenium species has a characteristic combination of leaf trichomes. In order to recognize the contribution of each parent in future studies of hybrids, characteristics of leaf trichomes of the following Parthenium species were studied: P. tomentosum, P. fruticosum, P. Schottii and P. rollinsianum. All species studied had two or more types of trichomes, and, in some species, trichomes of upper and lower epidermal surfaces were different. The prominent trichomes on upper epidermis of P. tomentosum and P. fruticosum were simple, uniseriate, conical trichomes, which also were observed on both epidermal surfaces of P. Schottii. Extremely long, narrow, simple, whiplike, trichomes formed a dense cover on both surfaces of P. rollinsianum and on the lower surfaces of P. tomentosum and P. fruticosum. Simple, uniseriate, cylindrical trichomes, and biseriate, glandular trichomes were observed in all four species.     

WOOD ANATOMY OF ILLICIUM (ILLICIACEAE): PHYLOGENETIC,ECOLOGICAL, AND FUNCTIONAL INTERPRETATIONS

Quantitative and qualitative features are reported for 23 collections of ten species of Illicium, sole genus of Illiciaceae. Vessel elements are long, thin-walled, and angular; perforation plates are scalariform and range from long to moderately long; vessel-ray pitting is scalariform to opposite. Tracheids bear fully bordered pits. Axial parenchyma is sparse, abaxial to vessels with some diffuse cells also present. Rays are both multiseriate and uniseriate; the former are lacking near the pith in some species. No erect sheathing cells are present on multiseriate rays, and procumbent cells become more abundant as stems increase in size. Four species from montane subequatorial highlands lack growth rings and helical sculpture in vessels; the remainder of Illicium species have these features. Notably narrow vessels and large numbers of vessels per sq. mm characterize the temperate species from northern limits for the genus, I. anisatum, I. floridanum, and I. parviflorum. Greater vessel density offers redundancy and greater safety and is correlated with greater frost and possibly greater fluctuation in moisture availability. These two ecological features are probably also related to the narrow vessel diameter, which may retard entry of air embolisms (lowered air entry values) in accord with the physiological considerations of Slatyer. Reduction of number of bars per perforation plate within Illicium is also correlated with the more northerly climates. An additional hypothesis for evolution of shorter vessel elements in dicotyledons is introduced: if, as claimed by Slatyer, air embolisms in vessels tend to stop at ends of vessel elements and thus do not disable entire vessels, shorter vessel elements would maximally localize air embolisms. Presence of helical sculpture and other forms of relief within vessels has been difficult to explain in conifers and dicotyledons; such features might help resist cavitations by increasing adhesion of water molecules to cell walls (hydration).     

Scalariform-to-simple transition in vessel perforation plates triggered by differences in climate during the evolution of Adoxaceae

Background and Aims Angiosperms with simple vessel perforations have evolved many times independently of species having scalariform perforations, but detailed studies to understand why these transitions in wood evolution have happened are lacking. We focus on the striking difference in wood anatomy between two closely related genera of Adoxaceae, Viburnum and Sambucus, and link the anatomical divergence with climatic and physiological insights.Methods After performing wood anatomical observations, we used a molecular phylogenetic framework to estimate divergence times for 127 Adoxaceae species. The conditions under which the genera diversified were estimated using ancestral area reconstruction and optimization of ancestral climates, and xylem-specific conductivity measurements were performed.Key Results Viburnum, characterized by scalariform vessel perforations (ancestral), diversified earlier than Sambucus, having simple perforations (derived). Ancestral climate reconstruction analyses point to cold temperate preference for Viburnum and warm temperate for Sambucus. This is reflected in the xylem-specific conductivity rates of the co-occurring species investigated, showing that Viburnum lantana has rates much lower than Sambucus nigra.Conclusions The lack of selective pressure for high conductive efficiency during early diversification of Viburnum and the potentially adaptive value of scalariform perforations in frost-prone cold temperate climates have led to retention of the ancestral vessel perforation type, while higher temperatures during early diversification of Sambucus have triggered the evolution of simple vessel perforations, allowing more efficient long-distance water transport.     

First record of Cercidiphylloxylon (Cercidiphyllaceae) from the Palaeocene of Fushun,NE China

Abstract Cercidiphylloxylon spenceri (Brett) Pearson is described from the Lizigou Formation, Palaeocene in China. The growth rings are distinct; pores are diffuse, solitary, with somewhat angular outlines in cross section; vessel elements long with long scalariform perforation plates; intervessel pitting is opposite to scalariform; fiber‐tracheids are present; axial parenchyma is scarce; rays are mostly biseriate and heterogeneous. All wood characters of the fossil specimen fall into the range of those of extant Cercidiphyllum (Cercidiphyllaceae). The finding is one of the earliest fossil wood records of Cercidiphyllaceae.     

AN OCCURRENCE OF CORDAITES IN THE UPPER PENNSYLVANIAN OF ILLINOIS

Cohen , Lila M., and Theodore Delevoryas . (Yale U., New Haven, Conn.) An occurrence of Cordaites in the upper Pennsylvanian of Illinois. Amer. Jour. Bot. 46(7): 545–549. Illus. 1959.—Cordaites validus a new cordaitean species from Calhoun, Illinois, is described. It is characterized by one or more vertical series of large, barrel-shaped parenchyma cells in association with the primary xylem, a short transition zone of primary xylem elements, extremely shallow uniseriate rays and generally uniseriate pitting. This species represents the first North American Cordaites shown to be endarch throughout.     

Vessel dimensions in liana and tree species of Gnetum (Gnetales)

Maximum vessel diameters were examined in the secondary xylem of stems of Gnetum of various sizes. One tree (G. gnemon) and 13 liana species were compared. In three species, vessel length distributions were determined by the latex paint method, and showed many short and fewer long vessels. Latex and compressed air methods, used to find the maximum vessel lengths, showed that maximum vessel lengths were similar for three species of Gnetum. In old stems, mean and maximum vessel diameters tended to be greater in lianas than in the tree species. The skewed distribution of vessel lengths and the trend of wider vessels in lianas as compared to trees were similar to those distributions and trends described previously for angiosperms. In random samples of macerated wood of three species, simple perforation plates were most common in vessel members of all species. Foraminate and modified foraminate perforations were less frequent. Average diameter of vessel members with either foraminate or modified foraminate perforations was less than for those with simple perforations. The resemblance of Gnetum vessels to those of angiosperm trees and vines is most likely a case of convergent evolution (homoplasy) in xylem characteristics.     

STUDIES IN THE FLORAL ANATOMY OF CLAYTONIA (PORTULACACEAE)

Claytonia virginica has a regular flower with two sepals, five petals with an equal number of stamens in positions opposite the petals and a many-seeded tricarpellate gynoecium with basal placentation. The flower has been interpreted as uniseriate, the putative sepals as bracts and the corolla as modified calyx lobes. Anatomical and developmental studies were undertaken to find evidence for the existence of vestigial or rudimentary parts whose existence would illuminate the true nature of the flower. Vascular and epidermal anatomy of sepals are both similar to that of leaves. Corolla and androecium develop basipetally and petals and stamens share common vascular traces in the lower part of the receptacle. Thus, in terms of both anatomy and development, evidence supports the conclusion that the perianth is essentially biseriate. Vestigial or rudimentary parts are not present which would alter the manifest design of the mature flower.     

Wood anatomy of Elaeagnaceae, with comments on vestured pits, helical thickenings, and systematic relationships

The secondary xylem of Elaeagnus, Hippophae, and Shepherdia is described and illustrated in detail. Shrubs and small trees of Elaeagnaceae have ring-porous or semi-ring-porous wood with simple perforation plates, vascular tracheids, fiber-tracheids, diffuse or rarely paratracheal axial parenchyma, and uni- or biseriate rays in Hippophae and Shepherdia, but wider rays in Elaeagnus. Walls of vessel elements, especially narrow ones, tracheids, or fiber-tracheids sometimes show helical thickenings; in a few instances these intergrade with small bud-like protrusions associated with pits. Scanning electron microscopy illustrates that small to vestigial vestures are present in all species studied, although nonvestured pits are also common. The analogous nature of vestures and helical thickenings is considered. Comparative wood anatomy suggests a rather isolated position of the family Elaeagnaceae; affinities with Rhamnaceae, Proteaceae, and Thymelaeaceae are discussed.     

Structure of the vascular cambium of varying age and its derivative tissues in the stem of Ficus rumphii Blume

AJMAL, S. & IQBAL, M., 1992. Structure of the vascular cambium of varying age and its derivative tissues in the stem of Ficus rumphii Blume. The cambial cells of Ficus rumphii and their derivatives vary in size and number with the age of the tree. The fusiform initials, vessel elements, sieve-tube members, xylem fibres and phloem fibres are relatively short in the terminal part of the stem axis, consistently longer down the stem reaching a maximum, and short again in the main trunk. The width of the respective cells shows a similar variation. The ray cell initials increase both in number and size, and form rays of varying dimensions. Uniseriate and biseriate cambial rays are abundant, while multiseriate rays are especially sparse in the young shoot. The proportion of uni- and biseriate rays falls in the lower part of the stem whereas that of multiseriate rays increases. Likewise, short cambial rays are abundant in young branches but their frequency decreases in the trunk region, leading to a rise of the tall ray population. The rays in the phloem and xylem regions reflect a similar variation pattern with certain fluctuations. The overall proportion of the rays increases in the older part of the axis, reaching a maximum tangential area in the trunk. The transectional area of vessel elements remains more or less constant down to the base after an initial increase in the terminal region, while the sieve-tube proportion tends to be constant in the basal region after a consistent gain from the tree top basewards.     

黑龙江苹果亚科5属14种植物导管分子形态结构研究

利用扫描电子显微镜对黑龙江苹果亚科5属14种植物导管分子的管腔微形态结构特征进行了比较研究。结果显示:(1)该亚科植物导管分子的管腔长度、宽度及端壁斜度角有较大的差别。(2)孔纹导管在该亚科植物种中均存在,网纹导管和螺纹导管仅见于苹果属和花楸属中。(3)导管分子管壁除苹果属及山楂属中的毛山楂、辽宁山楂外均有螺纹加厚。(4)纹孔的排列方式为互列式、对列式及互列、对列同时存在。(5)在所观察的植物中花楸、山荆子、无毛山楂导管端壁具单穿孔板和梯状穿孔板,其余种的导管端壁仅具单穿孔板。(6)导管纹孔膜残留现象普遍存在。研究表明,导管分子管腔的微形态结构特征,可为该亚科植物的系统演化提供形态学依据;导管分子微形态结构特征与其所处的环境存在一定的适应性。