ASCOCARPIC CENTRUM ONTOGENY OF SPECIES OF HYPODERMATACEAE OF CONIFERS. II

Ascocarpic studies of the ontogeny of Lophodermium nitens disclosed a type of development unlike that of all other species of Hypodermataceae occurring on conifer needles. For this reason the centrum of L. nitens is designated as Type III and is compared with Type I (Gordon, 1966). Because L. nitens produces its ascocarp in several tissues of various species of pine, the ontogeny of ascocarps in different locations is discussed and illustrated. The most significant ontogenetic feature of the ascocarp of L. nitens is a layer of hyaline cells in the primordium; this layer is meristematic and gives rise to all subsequent structures of the centrum.     

中国北部地区一些针叶树生斑痣盘菌

本文报道我国北部地区针叶树生斑痣盘菌目(Rhytismatales)真菌6属13种。其中哈尔滨散斑壳(Lophodermium harbinense Y.R.Lin)是新种,秋散斑壳(L.autumnale Darker)和雪松散斑壳(L.cedrinum Maire)为中国新记录种,其余诸种国内曾有过记录。对新种作了拉丁文、汉文描述及图解,对新记录种进行了简要记述,并记载了已知种的寄主新记录和地理新分布。     

A REINTERPRETATION OF THE ONTOGENY OF THE ASCOCARP OF SPECIES OF THE ERYSIPHACEAE

A study of four species of Erysiphaceae (Uncinula salicis, Podosphaera leucotricha, Erysiphe cichoracearum, and Microsphaera diffusa) revealed that the binucleate stages of the ascocarp are initiated in a similar manner to those of Diporotheca rhizophila Gordon & Shaw. The “appendages” developing on immature ascocarps are considered to be receptive hyphae. Appendages characteristic of mature ascocarps are produced much later. Lysis of certain centrum cells occurs, and asci are initiated from some of the remaining binucleate centrum cells. Resorption of centrum cells by the asci is supported by this investigation, corroborating Björling's earlier studies on Erysiphe graminis.     

ONTOGENY OF SEXUAL CONCEPTACLES IN A SPECIES OF BOSSIELLA (CORALLINACEAE)1

The first evidence of conceptacle formation in male and female plants of Bossiella californica ssp. Schmittii is the secretion of a cap below the epithallium. Subsequent development involves the disintegration of the upper enucleate parts of cortical cells below the center of the cap concomitant with the growth of tissue surrounding these cells. Protoplasts in the lower parts of these cortical cells recover and become initials of reproductive cells. Differentiation of each initial in female plants results in a supporting cells bearing 1 or 2, 2-celled carpogonial filaments, and in male plants results in a basal cell bearing 2 or 3 spermatangial mother cells which bud off spermatangia. Following fertilization, supporting cells fuse and form a broad, thin fusion cell from the upper surface of which gonimoblast (carposporangial) filaments arise.     

COMPARISON OF SHOOT APEX DYNAMICS AND EARLY LEAF ONTOGENY IN TWO SPECIES OF SARACA (LEGUMINOSAE)

Shoot apices of Saraca indica produce adult leaves that have 4 to 6 pairs of leaflets, whereas those of S. bijuga usually have only 2 pairs. In both species one leaflet pair is found during the juvenile phase. Juvenility lasts many plastochrons in S. bijuga but is restricted to a few in S. indica. The shoot apical meristems of these two taxa are similar in structure, cell number, and cell size; however, the shoot apex of Saraca bijuga is slightly more stratified, having 2–3 tunica layers as opposed to 1–2 in S. indica. For most of the plastochron the apical meristem in both species is situated laterally at the base of the most recently formed leaf. A newly forming primordium and its internode shift the apical meristem upward unilaterally; the meristem passes through a brief apical dome stage and becomes positioned 180° from its origin at the beginning of the plastochron. Hence, there is a true pendulum meristem in both species. In S. bijuga the maximum length of the youngest leaf primordium, just prior to the formation of its successor, is twice that of S. indica. The internodes immediately below the shoot apex and the axillary buds develop more rapidly in S. bijuga than in S. indica. It is suggested that the bijugate leaf of S. bijuga represents a case of neoteny in plants.     

TWO NEGLECTED ASPECTS OF FOSSIL CONIFERS

Most conifers, living and fossil, drop their foliage in one of two natural ways. Either each leaf is abscised separately, or intact leafy shoots are abscised. Thus, a fossil leafy shoot of a leaf-dropping species is an unusual specimen, and is the result of premature, violent removal, as by storm. Any reproductive organs it bears are likely to be immature. This idea, applied to the ovules of Taxus jurassica Florin leads to their reinterpretation: they prove unlike Taxus, but rather, like Amentotaxus. A few living conifers drop their leaves or leafy shoots at the end of each summer. There may be evidence that a fossil was deciduous. Phyllotaxis has seldom been examined closely in fossil conifers but can be clearly observed even in compressed specimens. Three main kinds occur: 1) Leaves or cone scales are attached singly in a helix (spiral) which is usually very regular. 2) Leaves are attached two (or more) at a node and those of the next node alternate strictly; if there are pairs, the next pair is at 90° decussation. 3) Leaves are in opposite pairs but the next pair is at an angle of less than 90°, and the leaves form a double helix or bijugate spiral. In fossils all three kinds can be subdivided according to the numbers of oblique rows (parastichies) rising to the right and left, in relation to the diameter of the organ. Torreya gracilis Florin (from the Jurassic) proves to have the same phyllotaxis, a double helix, as that found in modern Torreya shoots. But Florin's Taxus jurassica has its leaves in decussate pairs, unlike Taxus, but rather, like Amentotaxus. For this and other reasons it is here renamed Marskea jurassica (Florin) comb. cnov.     

ONTOGENY OF ANGIOTENSIN II RECEPTORS

Aside from the well known role of angiotensin II (Ang II) in blood pressure regulation and fluid homeostasis, accumulating evidence suggests that the octapeptide hormone also plays a role in growth and development. There are two major classes of Ang II receptors (AT₁and AT₂) which mediate Ang II action. Both classes are members of the large superfamily of seven transmembrane domain spanning receptors. Fetal tissue express high levels of AT receptors. Throughout fetal and postpartum life, the AT₁and AT₂tissue distribution changes dramatically. The evolution of each receptor type is distinct and varies according to the organ. Thus, the different patterns of temporal expression of each receptor class could be related to various roles that Ang II may play during development.     

THE CENTRUM OF THE SOOTY MOLD ASCOMYCETE LIMACINULA SAMOENSIS

Centrum development in the sooty mold Ascomycete Limacinula samoensis von Hoehnel emend. Reynolds proceeds in an ascostroma which begins as a small cushion of somatic tissue and enlarges by multiplication of cells in an apical region and by cell enlargement. A two-layered ascocarp wall initially surrounds a pseudoparenchymatous core into which the bitunicate asci protrude. Interascal strands of pseudoparenchymatous tissue disintegrate at maturity of the ascocarp. An apical meristem eventually culminates activity with formation of a short ostiolate neck. Centrum development is homologous to the Dothidea type. The centrum development of other capnodiaceous fungi is reviewed.     

COMPARATIVE ASPECTS OF THE ONTOGENY OF TASTE

Pigs are proposed as a useful laboratory model for the investigationof taste preferences and other controls of ingestive behaviorin the newborn. Suckling pigs can be easily trained to feedthemselves from an artificial feeding apparatus so that intakecan be measured directly. In this manner preferences for glucose,sucrose, fructose and lactose were found in pigs 3 wk of age.The preference threshold for glucose is considerably higherthan that reported for more mature pigs. Taste aversion wasdemonstrated in suckling pigs 2 wk of age. After the taste ofglucose had been paired with LiCl injection, poisoned pigs didnot show the strong glucose preference shown by control pigs.In addition to oropharyngeal controls of intake, gastrointestinalcontrols of intake in the newborn pig were investigated.Loadsof milk or 5% glucose, but not 0.9% NaCl, given by gavage depressedsubsequent intake in piglets 1 wk of age. Caloric or glucostaticmechanisms, but not volume alone, appear to be involved in satietyin the newborn pig. ^*Supported by USPHS Special Fellowship 5F03 AM55321-02 to K.A.H.Request for reprints should be sent to Dr. K. A. Houpt, Dept.of Physiology, N.Y.S. College of Veterinary Medicine, Ithaca,New York 14853, U.S.A.