. Dansk botanisk arkiv. Plants; Plants -- Denmark. 132 Dansk Botanisk Arkiv, Bd. 3. Nr. Peyssonnelia (Cru- oriella) simulans nov. spec. Section throug tlie margin of thailus. t. topcell or apical cell; the one row of inferior cells constitute the hypothal- lus, the ascending, still short cellrows, the perithallus. (200:1). it may be higher {P. (Eup.) simulans), but it is always less high than the apical cell (Fig. 140). In a few other species {P. (Eup.) rubra) the topcell or the cells following may be longer than high; it divides just like the short one by an oblique cellwall on
. Dansk botanisk arkiv. Plants; Plants -- Denmark. 132 Dansk Botanisk Arkiv, Bd. 3. Nr. Peyssonnelia (Cru- oriella) simulans nov. spec. Section throug tlie margin of thailus. t. topcell or apical cell; the one row of inferior cells constitute the hypothal- lus, the ascending, still short cellrows, the perithallus. (200:1). it may be higher {P. (Eup.) simulans), but it is always less high than the apical cell (Fig. 140). In a few other species {P. (Eup.) rubra) the topcell or the cells following may be longer than high; it divides just like the short one by an oblique cellwall on its longitu- dinal axis into two segments. The outer one grows until it has reached its for- mer size and then divides again. The in- ner segment will grow too, and may first divide again by a vertical cellwall; if this is the case, the third or even the fourth cell after repeated division, increases in height and then divides by a hori- zontal wall into two often unequal portions. The inferior one retains the height it had at the moment of divi- sion of the apical cell; it communicates with its neighbouring hypothallic cells of the same filament through the primary cen- tral pore; the upper portion is the mother cell of the ascending filaments. I thought at first that these differences in growth oi the apical cell might coincide with the branching of the hypo- thallus, but this is not the case. I have found the short, high apical cell in species belonging to the subgenus Eupeyssonnelia as well as to the subgenus Cruoriella and in both subgenera the longer and less high apical cell. Therefore I consider this character only useful as a specific one, but as a good one, for great as the va- riability of the Peyssonnelia may be, I can not imagine that a top- cell as in Fig. 140 can grow into a topcell like Fig. 144. When treating of the Peys- sonnelia of the Siboga Expedition, I hope to be able to give some more details about the growth of the apical part of these algæ, but this s
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