ON THE ANATOMY AND MORPHOLOGY OF LATERAL BRANCH SYSTEMS OF ARCHAEOPTERIS

A large collection of specimens, consisting primarily of Archaeopteris macilenta, forms the basis for an anatomical and morphological study of the lateral branch systems. Emphasis is placed on the main axes of the branch systems, which are found to be characterized by a variable number of orthostichies of lateral appendages, ranging from 7 to probably 11. The number of orthostichies seems to correspond to the number of ribs of the stele. There may be an equal number of rows of leaves on either side of the plane in which the two rows of lateral branches lie, or one side may have one or two more leaf orthostichies than the other. In all specimens for which both part and counterpart were available, however, there is a greater density of leaves on one side (hypothesized to be the adaxial) than on the other, caused primarily by an apparent abortion of leaf primordia early in development on the side of least density. Leaves and branches occur in the same ontogenetic spiral and in one specimen comprise a ‘phyllotaxis’ of 2/9 and contact parastichies of 5 + 9. On both the main and lateral axes, leaves are characterized by long, decurren bases which essentially ensheath the axrs on which thay are borne. Phyllotaxis and the correlated stelar form apparently vary considerably within Archaeopteris. It is suggested that Archaeopteris was more closely related to the coniferophytes than to any other gymnosperms.     

SOME EFFECTS OF NITROGEN NUTRITION ON THE MORPHOLOGY AND ANATOMY OF MARROW-STEM KALE

Marrow-stem kale plants grown on plots receiving frequent additions of sulphate of ammonia showed a 40% increase in length of internode and a 25% increase in number of nodes per plant, and the leaf size was increased by between 50 and 70% over plants in plots receiving no N fertilizer. Leaves of kale continue to increase in area until they turn yellow, and the high N leaves showed a greater rate of increase in area at every stage in the life of the leaf.
Various features of leaf structure, such as stomatal index, and thickness of palisade and mesophyll, were unaffected by N treatment. The size of the epidermal cells of the leaves was very variable, and although the high N leaves showed a 12% increase in area per epidermal cell over the low N leaves, this difference is not statistically significant. The increased area of the high N leaves can therefore be attributed mainly to increased cell division during the life of the leaf. Only a very slight increase in rate of cell division is necessary to produce the observed effect.
The greater leaf area of the high N plants can be attributed mainly to increased size of individual leaves, but there was also a significantly greater number of living functional leaves per plant on the high N plants; at 23 weeks from sowing the high N plants had an average of 13.4 living leaves, while the low N plants had only 11.7 living leaves per plant.
There was an appreciable degree of N succulence in the high N kale leaves, which showed a 2% greater moisture content than the low N leaves.
A seasonal drift in epidermal cell size, palisade thickness, and total leaf thickness, is shown to be fully significant, statistically. Marked variations in stomatal frequency are barely significant at the 5% level.     

THE COMPARATIVE MORPHOLOGY OF THE CANELLACEAE. II. ANATOMY OF THE YOUNG STEM AND NODE

The anatomy of the young stem and node was investigated in 12 species representing all 6 genera of the Canellaceae. The salient anatomical features of this family are as follows: (1) the primary vascular system is pseudo-siphonostelic; (2) druse-type calcium oxalate crystals and ethereal oil cells are characteristic of the parenchymatous tissues; (3) all members of the family exhibit trilacunar nodes; (4) the periderm is superficial in origin with characteristic U-shaped thickened cells; and (5) the sieve-tube members are of a primitive type with obliquely oriented end walls and many unspecialized sieve areas. On the basis of this anatomical investigation, the conclusion that the Canellaceae has a general ranalean affinity is strengthened.     

THE ANATOMY AND THREE-DIMENSIONAL MORPHOLOGY OF ANNULARIA HOSKINSII SP. N.

Foliage attached to calamitean shoots is described from coal ball petrifactions of Middle and Late Pennsylvanian age. Leaves correspond to the compression-impression genus Annularia and thus represent the first attached members of this genus to be recognized as petrifactions. Individual leaves contain a single unbranched vascular bundle flanked by wide lateral laminar areas which occupy more than half the leaf cross sectional area. Stomata are confined to broad bands within concave furrows which parallel the vascular bundle on the abaxial leaf surface. Epidermal cells within these furrows are in rows aligned obliquely to the leaf axis, and the rows angle outward at a slight angle towards the leaf margin. Convolutions of the leaf-bearing axes result from nodal diaphragms which are oblique to the shoot axis. Whorled leaves apparently radiate outward in the plane of each obliquely positioned nodal diaphragm. This petrified material helps explain the apparent flattening of entire nodal diaphragms and leaf whorls within the same plane as seen in compression specimens. Annularia hoskinsii sp. n. is proposed, and the systematic position of structurally preserved Annularia foliage relative to the genus Dicalamophyllum is discussed.     

STUDIES OF PALEOZOIC FERNS. THE MORPHOLOGY,ANATOMY, AND TAXONOMY OF ANKYROPTERIS GLABRA

Eggert , Donald A. (Yale U., New Haven, Conn.) Studies of Paleozoic ferns. The morphology, anatomy, and taxonomy of Ankyropteris glabra. Amer. Jour. Bot. 46(7): 510–520. Illus. 1959.—This is a morphological and taxonomic study of the American specimens of Ankyropteris, with the exception of A. hendricksi, that previous to this time have been referred to A. grayi, originally a Lower Carboniferous species from England, and to A. glabra, a Middle-Pennsylvanian form from Booneville, Indiana. The problem of the separation of these two closely allied species is discussed, and the original criteria for separation are questioned, on the basis of four specimens described in the present paper. The specimens are from West Mineral, Kans. and Shuler Mine in Iowa. They all have been referred to A. glabra and show extreme plasticity of several features of the plant that is correlated with the size of the stem. The major points of difference between A. glabra and A. grayi are now thought to be the presence of distantly spaced nodes in A. glabra, in contrast to closely spaced ones in A. grayi, and the presence of a small amount of mixed tissue in the stele of A. glabra, compared to a large amount in A. grayi. Well preserved axillary branches were found, whose morphology is typically that of the parent stem. It is suggested that the axillary branches were well developed in the species, and that, therefore, several orders of branching may be present in the American material. Successive orders of branching show diminution and simplification which is interpreted as an expression of the presence of determinate growth in the cauline systems of the plant, an ontogenetic pattern that is not commonly found in living forms.     

STUDIES ON THE LEAF OF POPULUS DELTOIDES (SALICACEAE): MORPHOLOGY AND ANATOMY

Mature field- and growth-chamber-grown leaves of Populus deltoides Bartr. ex Marsh. were examined with light and scanning electron microscopes to determine their vasculature and the spatial relationships of the various orders of vascular bundles to the mesophyll. Three leaf traces, one median and two lateral, enter the petiole at the node. Progressing acropetally in the petiole these bundles are rearranged and gradually form as many as 13 tiers of vascular tissue in the petiole at the base of the lamina. (Most leaves contained seven vertically stacked tiers.) During their course through the midrib the tiers “unstack” and portions diverge outward and continue as secondary veins toward the margin on either side of the lamina. As the midvein approaches the leaf tip it is represented by a single vascular bundle which is a continuation of the original median bundle. Tertiary veins arise from the secondary veins or the midvein, and minor veins commonly arise from all orders of veins. All major veins–primaries, secondaries, intersecondaries, and tertiaries–are associated with rib tissue, while minor veins are completely surrounded by a parenchymatous bundle sheath. The bundle sheaths of tertiary, quaternary, and portions of quinternary veins are associated with bundle-sheath extensions. Minor veins are closely associated spatially with both ad- and abaxial palisade parenchyma of the isolateral leaf and also with one or two layers of paraveinal mesophyll that extend horizontally between the veins. The leaves of growth-chamber-grown plants had thinner blades, a higher proportion of air space, and greater interveinal distances than those of field-grown plants.     

STUDIES ON THE LEAF OF AMARANTHUS RETROFLEXUS (AMARANTHACEAE***): MORPHOLOGY AND ANATOMY

The leaf of Amaranthus retroflexus L. was examined with the light microscope to determine its vasculature and the spatial relationship of the vascular bundles to the mesophyll. Seven leaf traces enter the petiole at the node and form an arc that continues acropetally in the petiole as an anastomosing system of vascular bundles. Upon entering the lamina, the arc of bundles gradually closes and forms a ring of anastomosing bundles that constitutes the primary vein, or midvein, of the leaf. As the midvein progresses acropetally, branches of the bundles nearest the lamina diverge outward and continue as secondary veins toward the margin on either side of the lamina. Along its course the midvein undergoes a gradual reduction in number of bundles until only one remains as it approaches the leaf tip. Tertiary veins arise from the secondaries, and minor veins commonly arise from all orders of major veins, as well as from other minor veins. All of the major veins are associated with rib tissue, although the ends of the tertiaries may resemble minor veins, which are completely encircled by chlorenchymatic bundle sheaths and mesophyll cells that radiate out from the sheaths. A specialized minor vein, the fimbrial vein, occurs just inside the margin of the leaf. Most of the mesophyll cells—the so-called “Kranz mesophyll cells”—are in direct contact with the bundle sheaths, but some—the so-called “nonKranz mesophyll cells”—lack such contact. Non-Kranz mesophyll cells are especially prominent where they form a network of mostly horizontally oriented cells just above the lower epidermis. Guard cells of both the upper and lower epidermis are spatially associated with nonKranz mesophyll cells.