. The structure and development of mosses and ferns (Archegoniatae). siotium differs from all other known Acrog-ynse in having a two-sided apical cell, instead of the typicaltetrahedral one—(Goebel (21), p. 287). The Sex-organs The plants in Porella are strictly dioecious and the two sexesare at once recognisable. The males are smaller, and bearspecial lateral branches which project nearly at right anglesfrom the main axis, and whose closely imbricated light green in THE JUNGERMANNIALES 105 leavei. make them conspicuous. At the base of each of theleaves is a long-stalked antheridium, large eno
. The structure and development of mosses and ferns (Archegoniatae). siotium differs from all other known Acrog-ynse in having a two-sided apical cell, instead of the typicaltetrahedral one—(Goebel (21), p. 287). The Sex-organs The plants in Porella are strictly dioecious and the two sexesare at once recognisable. The males are smaller, and bearspecial lateral branches which project nearly at right anglesfrom the main axis, and whose closely imbricated light green in THE JUNGERMANNIALES 105 leavei. make them conspicuous. At the base of each of theleaves is a long-stalked antheridium, large enough to be readilyseen with the naked eye. The development of the antheridium may be easily tracedby means of sections made parallel to the surface of the the apex (Fig 50, C) is an apical cell much like that in thesterile branches, but with the outer face more convex. Thedivisions in the segments are the same as there, but the wholebranch remains more slender, and the hairs at the base of theleaves are absent. The antheridia arise singly from the bases. Fig. 52.—P<?f^//o Bolanderi. Successive stages of the young antheridium in median longitudinal section, X6oo. of the leaves, close to where they join the stem, and are recog-nisable in the fourth or fifth youngest leaf (Fig. 50, C, <^).The antheridial cell assumes a papillate form, and divides bya transverse w^all into an outer and inner cell, and the formerdivides by a similar wall into two cells, of which the upper oneis the mother cell of the antheridium, and the other the first wall in the antheridium itself is vertical (Fig. 52, B),and divides it into two equal parts. Each of these is nowdivided by two other intersecting walls, best seen in cross-sec- io6 MOSSES AND FERNS CHAP. tion (Fig. 53, A), which separate a central cell, nearly tetra-hedral in form, from two outer cells. In the complete separa-tion of the central cell by these first two walls, Porella appearsto differ from the other Junge
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