The structure & development of the mosses and ferns (Archegoniatae) . nia ; //,ventral scales ; B, median section through a pore, showing the assimilating cells (cl) below, X300. pressed (Fig. 17, C), so that this may account for Janczewskis^error in stating that the number was always four, as the nucleiin unstained sections might be very easily overlooked. Thecover cells are somewhat smaller than in Riccia and do notusually undergo as many divisions, there being seldom more ^ Janczewski (i), p. 386. 54 MOSSES AND FERNS CHAP. than six in all. In Targionia (Fig. 21, A), and Strasburger^observed
The structure & development of the mosses and ferns (Archegoniatae) . nia ; //,ventral scales ; B, median section through a pore, showing the assimilating cells (cl) below, X300. pressed (Fig. 17, C), so that this may account for Janczewskis^error in stating that the number was always four, as the nucleiin unstained sections might be very easily overlooked. Thecover cells are somewhat smaller than in Riccia and do notusually undergo as many divisions, there being seldom more ^ Janczewski (i), p. 386. 54 MOSSES AND FERNS CHAP. than six in all. In Targionia (Fig. 21, A), and Strasburger^observed the same in Alarchantia, the ripe egg shows a distinct receptive spot, that is, the upper part of the unfertilisedegg is comparatively free from granular cytoplasm, while thelower part, about two-thirds in Targionia, is much more denselygranular. The nucleus is not very large and has very littlechromatin. The nucleolus is large and distinct and stains veryintensely. As the archegonium of Targionia matures, itsneck elongates rapidly and bends forward and upward, no. Fig. 17.—Targionia hypophylla (L.). A, Longitudinal section of the apex of the thallus, with youngarchegonia (ar), x 525 ; x, the apical cell ; B, joung; C, older archegonium in longitudinalsection ; D, cross-section of the archegonium neck, X 525. of the the archegonium archegonium IS neck isupon the doubt an adaptation to facilitate the entrance of the sper-matozoid. A similar curvingobserved in other forms wherelower side of the receptacle. After an archegonium (or sometimes several of nearlyequal age) is fertilised, the growth in length of the thallus stops,but there is a rapid lateral growth with results in the formationof two valves, which meet in front much like the two parts ofa bivalve shell, and this involucre completely encloses theyoung growing sporogonium. ^ Strasburger (2), p. 418. Ill MA RCHANTIEJE 55 In the simplest cases, where the archcgonia are borne upona receptacle ^ which is raised upon a sta
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