A morphological study of some members of the genus Pallavicinia . Pallavicinia Zollingeri. A. Segment of the frond of an antheridial plant, x 25 (about). B. A portion of A, more highly magnified. C. Longitudinal section of the shoot, passing through an antheridium, and showing the strand of conducting tissue. D. Cross-section of a segment of the frond, showing the position of the antheridia on the dorsal surface of the midrib. METHODS II The cells of the ventral part of the midrib have thick walls in whichare pits elongated transversely. These pits are in lines extending roundthe cell, and for
A morphological study of some members of the genus Pallavicinia . Pallavicinia Zollingeri. A. Segment of the frond of an antheridial plant, x 25 (about). B. A portion of A, more highly magnified. C. Longitudinal section of the shoot, passing through an antheridium, and showing the strand of conducting tissue. D. Cross-section of a segment of the frond, showing the position of the antheridia on the dorsal surface of the midrib. METHODS II The cells of the ventral part of the midrib have thick walls in whichare pits elongated transversely. These pits are in lines extending roundthe cell, and forming partial spirals, this being perhaps due to the longi-tudinal growth of the cell (Fig. 3, D, E). These cells, which are pre-sumably conducting cells, have very little protoplasmic contents, thusagreeing with Tansleys description of the corresponding tissue in othermembers of the genus [1]. The cells of the cortical tissue of the rhizomecontain many starch granules, in this respect recalling Cavers figures ofMorkia flowtowimia [2]. Fig. 5. Pallavicinia fronds of female plants, x 2. The base of the aerial shoot, or frond, like the rhizome of which it isthe continuation, is quite destitute of the wing-like lamina found in theexpanded portion of the frond. The cylindrical stalk, as it ascends, be-comes gradually flattened dorsi-ventrally and develops a narrow wingon either side which widens until it forms the beginning of the expanded,fan-shaped lamina of the frond. The first dichotomy occurs when theyoung frond is 3-4 cm. in height. The forking is repeated from two tofour times, and there thus results the palmately divided leaf-like shoot, theslender central strands of the delicate segments simulating almost exactlythe venation of a true leaf. In the archegonial plants these fan-shaped 12 GENUS PALLAVICINIA fronds are about cm. in width (Fig. 5). In the male plants they aresomewhat smaller. The apex of each segment is indented, and the mar-gin is wavy, w
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Keywords: ., bookauthorcampbelldouglashought, bookcentury1900, bookdecade1910
