DEVELOPMENT OF NORMAL AND SEEDLESS ACHENES IN CICHORIUM INTYBUS (COMPOSITAE)

Cross- and partially cross-pollinated capitula of Cichorium intybus (Compositae, Lactuceae) were examined for a study of normal and seedless fruit development respectively. Embryos develop according to the Asterad pattern, and the free-nuclear endosperm becomes cellular 15–17 hrs after pollination. A zone of disorganized cellular material surrounds the embryo sac at anthesis, and, in normal achenes, this zone expands as the seed develops. Initially the developing seed elongates and comes into contact with the top of the ovary by 48 hrs. In contrast to this pattern, the ovule in developing seedless achenes degenerates within 72 hrs. Irregularities, such as an abnormally proliferating endothelium, embryo formation without endosperm, and endosperm formation without an embryo often accompany this degeneration. Differentiation of the pericarp in seeded achenes begins between 48 and 72 hrs, starting at the apex and proceeding basipetally; in seedless fruits the process is similar though initiated somewhat later. The normal pericarp at maturity exhibits a pigmented exocarp, a broad mesocarp of thick-walled lignified cells, and a tenuous endocarp. In seedless achenes the fruit coat is similar except that the exocarp is colorless and the cells of the mesocarp are relatively small.     

ONTOGENY AND CYTOCHEMISTRY OF ALKALOIDAL VESICLES IN LATICIFERS OF PAPAVER SOMNIFERUM L. (PAPAVERACEAE)

Development of alkaloidal vesicles in laticifers of opium poppy, Papaver somniferum L., was investigated at the ultrastructural level. Laticifer initials possessed abundant endoplasmic reticulum throughout their dense cytoplasm. During differentiation the endoplasmic reticulum organized into long, folded sheets that were parallel to the longitudinal walls along the periphery of the cell. Vesicles appeared to be derived from dilation of endoplasmic reticulum. This relationship was confirmed through cytochemical data obtained with zinc iodide-osmium tetroxide and osmium tetroxide impregnation. Alkaloidal vesicles had electron-dense regions or caps that occurred early in laticifer differentiation, but these caps became less conspicuous in mature cells. Caps appeared to be derived from small particles which condensed along the inner surface of the vesicle membrane and subsequently accumulated at one or two positions along the membrane of the vesicle.     

ONTOGENY AND STRUCTURE OF THE SECONDARY PHLOEM IN EPHEDRA

The secondary phloem in Ephedra is atypical of the gymnosperms in general and exhibits several angiosperm-like characteristics. The ray system of the conducting phloem consists of parenchymatous, multiseriate rays. The axial system contains parenchyma cells, sieve cells, and unusual albuminous cells reminiscent of the specialized parenchyma cells found in some angiosperms. These cell types may intergrade with each other. P-protein in the developing sieve element appears early in the form of a single, ovoid slime body. Later, smaller slime bodies appear and quickly disperse. In the mature sieve element the single, ovoid slime body is lost, and P-protein is then evident in the form of a parietal cylinder, thread-like strands, amorphose globules, or a slime plug. Necrotic-appearing nuclei are commonly found in mature sieve cells.     

ONTOGENY AND STRUCTURE OF THE SECONDARY PHLOEM IN PYRUS MALUS

Evert , Ray F. (U. Wisconsin, Madison.) Ontogeny and structure of the secondary phloem in Pyrus malus. Amer. Jour. Bot. 50(1): 8–37. Illus. 1963.—The secondary phloem of apple consists of sieve-tube elements, companion cells, phloem parenchyma cells, fiber-sclereids, and ray parenchyma cells. The sieve-tube elements are generally long, slender cells with very oblique end walls and much-compounded sieve plates. All sieve-tube elements initially possess nacreous thickenings. Similar wall thickenings were observed in the differentiating fiber-sclereids and xylem elements. Of the 245 sieve-tube elements critically examined, 242 were associated with companion cells. All of the companion cells were shorter than their associated sieve-tube elements. Young companion cells possess slime bodies which later become dispersed. Callose is often found on the sieve-tube element side of the common wall between sieve-tube element and companion cell. In several collections, callose was found on both sides of that wall. The parenchyma cells are of 3 types: crystal-containing cells; tannin-and/or starch-containing cells; and those with little or no tannins or starch. Any type parenchyma cell may be on to genetically related to a sieve-tube element, that is, may be derived from the same phloem initial as the sieve-tube element. Morphologically, the phloem parenchyma cells intergrade with the companion cells, the tannin- and starch-free parenchyma cells often being difficult to distinguish from companion cells. Most of the tannin- and starch-free parenchyma cells collapse when the contiguous sieve-tube elements become nonfunctional. The fiber-sclereids arise from parenchyma cells which overwinter on the margin of the cambial zone and differentiate in nonfunctional phloem.     

LIGHT MICROSCOPE INVESTIGATION OF SIEVE-ELEMENT ONTOGENY AND STRUCTURE IN ULMUS AMERICANA

At maturity the sieve elements of Ulmus americana L. contain a parietal network of very fine strands of slime which is continuous from one sieve element to the next through the sieve-plate pores. Upon injury this parietal network, which is derived from the slime bodies of immature sieve elements, sometimes becomes distorted into longitudinally oriented strands. Some of these strands frequently extend the length of the cells and often are continuous from one sieve element to the next through the sieve-plate pores. At times past such strands have erroneously been interpreted as normal constituents of the mature sieve-element protoplast. Many mature sieve elements of U. americana contain nuclei, which apparently persist for the life of the sieve elements. In addition, some evidence has been found in mature sieve elements for the presence of a membrane which delimits the parietal layer of cytoplasm, including its network of slime strands, from the vacuolar region of the cell.     

ONTOGENY AND STRUCTURE OF CONIFEROUS SIEVE CELLS

Studies of the secondary phloem of 6 species of conifers revealed that mature sieve-cell protoplasts contain internal strands which are derived ontogenetically from slime bodies of immature cells. These strands, each measuring about 0.3 μ in diameter, traverse the cell and run from cell to cell through sieve-area pores. Coniferous sieve cells have much in common—both ontogenetically and structurally—with dicotyledonous sieve-tube members.     

ASPECTS OF CONE AND OVULE ONTOGENY IN CRYPTOMERIA (TAXODIACEAE)

The axillary complex of female cones of Cryptomeria is initiated as a tangentially extended triangular structure with a rounded apex. It is bilaterally symmetrical. Structures interpreted as prophylls are differentiated first, but they become insignificant in later development. They are succeeded by two successive pairs of lobes, each lobe being the common primordium for an adaxial ovule and a tooth. The ovule initially much exceeds the tooth. The apex of the complex has a diversity of fates and may differentiate as an ovule-tooth pair. A one-to-one relation between teeth and ovules may be lost by abortion of ovules. The initial relation between teeth and ovules is obscured in later development due to extension of tissues at the base of the complex associated with considerable enlargement of the teeth. Histogenesis of the various parts is described, together with the vascular system. There is a vascular supply to the tooth but not the ovule. The results support a direct comparison with the extinct transition conifers Pseudovoltzia and Aethophyllum but do not fully support Florin's generalized model for the arrangement of parts in the axillary complex of conifers.     

THE OCCURRENCE AND BEHAVIOR OF B-CHROMOSOMES IN ASTRANTHIUM INTEGRIFOLIUM (COMPOSITAE)

Plants of Astranthium integrifolium (Michx.) Nutt. from Oklahoma proved to have a large B-chromosome which was morphologically similar to the smaller A-chromosomes. It was eliminated from some of the progeny of selfed plants. Structural modifications in the B-chromosome were observed. These observations are compared with ones obtained by previous workers, both for this species and in other genera.     

VARIATION AND LOCALIZATION OF FLAVONOID AGLYCONES IN HELIANTHUS ANNUUS (COMPOSITAE)

Flavonoid aglycone variation within Helianthus annuus, a species widely distributed throughout North America, was analyzed. Flavonoid aglycones of H. annuus consist of two types, flavones and chalcones. The flavone aglycones are sequestered in glandular trichomes that occur on both leaf surfaces, whereas the chalcone aglycones appear to be incorporated in the waxy leaf cuticle. Considerable variation in flavonoid profile was observed with some plants exhibiting as few as one, and others as many as seven of the eight aglycones detected. No definable phytogeographic patterns were observed for this flavonoid variation. Flavonoid aglycone variation also did not differentiate the infraspecific taxa within H. annuus.     

菊苣薄层培养花芽,营养芽分化中内源激素的动态变化

菊苣（Ｃｉｃｈｏｒｉｕｍ ｉｎｔｙｂｕｓＬ．）花梗薄层细胞培养于ＭＳ附加ＮＡＡ 和ＢＡ 或ＩＡＡ 和ＢＡ 的ＭＳ培养基上有花芽或营养芽分化． 花芽分化中内源ＩＡＡ、ＤＨＺ＋ ＤＨＺＲ、ｉＰＡ 含量明显增加,而Ｚ＋ ＺＲ变化不明显．营养芽分化中内源细胞分裂素含量增加明显,而ＩＡＡ 在培养前７ ｄ 含量下降,随后有所增加,在原基形成时含量达原初水平的２／３． 可见,花芽分化比营养芽分化所需内源ＩＡＡ／ＣＴＫ 比值要高     

REACTIONS OF ALKALOID AND HISTOCHEMICAL INDICATORS IN LATICIFERS AND SPECIALIZED PARENCHYMA CELLS OF CATHARANTHUS ROSEUS (APOCYNACEAE)

Chromic acid, iodine-potassium iodide and Dragendorff reagent were employed to identify reactive cells that may indicate sites of alkaloid accumulation in fresh tissues and latex of C. roseus. Laticifers in all parts of the mature plant and certain parenchyma cells in the cortex and pith regions accumulated reaction products of these alkaloid indicators. These same cells showed primary fluorescence, accumulated vital dyes and lipid indicators in excess of other cells, and exhibited a more intense nadi reaction than other cells. Tests on fresh tissues are interpreted to indicate possible qualitative and quantitative differences in alkaloid content between subterranean and aerial portions of the plant and between mature and immature tissues. These studies showed that reactive products are unevenly distributed in cells and organs of the plant and can be microscopically detected only in laticifers and specialized parenchyma cells.     

ONTOGENY,HISTOCHEMISTRY AND FINE STRUCTURE OF CELLULAR INCLUSIONS IN VEGETATIVE CELLS OF ANTITHAMNION DEFECTUM (CERAMIACEAE,RHODOPHYTA)1

The ultrastructure and histochemistry of developing and mature cell inclusions in vegetative cells of Antithamnion defectum Kylin were examined. Those studied were chloroplast inclusions, cytoplasmic crystals and spherical bodies within the vacuole. Chloroplasts of mature vegetative cells contain an interthylakoidal, apparently noncrystalline deposit of undetermined chemical identity. The bodies are parallel to the long axis of the plastid, are square (0.13 μm) in cross-section, and up to 3 μm long. Spherical vacuolar bodies (0.5–1.5 μum diam) are formed during early stages of vacuole formation by accumulation of protein deposits in swelling endoplasmic reticulum (ER) cisternae. Swelling of smooth ER contiguous to the ER containing the deposits results in the vacuole enclosing the spherical bodies. In mature cells, vesicles appear to be secreted into the preformed vacuole. Cytoplasmic proteinaceous crystalloids develop without a bounding membrane and may serve as protein reserves.