278 



EMBETOGENY IN LTCOPODIACaE. 



Lycopodiacese, Club Mosses (fig. 497), have sporangia which are 

 either all alike as in Lycopodium, or of two forms as in SelagineUa. 

 The dimorphic sporangia consist of micro-sporangia (fig. 498), 

 (/i/x^o's, small), containing numerous granules (microspores or antke- 

 ridia), (fig. 499), and macrosporangia (fig. 500), (/iaxgog, long), 

 called by some megasporangia (//^eyag, great), or oophoridia (aihv, 

 an egg, pog'eia, I bear), of a large size containing often four macro- 

 spores or megaspores, in the interior of which a cellular prothallus 

 is formed (fig. 501, p), on which archegonia are developed (fig. 



Fig. 502. 



Fig. 503. 



502 a). In the microspores of Isoetes and Lycopodium there is a 

 sort of male prothallium bearing antheridia with spermatozoids. No 

 germination has been observed in the microspores of the genus Lyco- 

 podium. The process of impregnation in Lycopodiacese is supposed 



Fig. 498. Antheridium of a Club-Moss (Lycopodivm), containing microspores, whicii are 

 cells containing spermatozoidal cellules, as seen in fig. 499. Fig, 499. Small spore (pollinic 

 spore) of a Lycopod {Selagmdla helvetica), bursting and discharging cellules, c, containing 

 spermatozoids. Fig. 500. Oophoridium or macro-sporangium of a Club-Moss (Lycopodivm), 

 opening and showing four large spores in its interior. These macrospores or megaspores 

 contain a cellular prothallium or endothallium in their interior, bearing archegonia. 

 Fig. 501. Macrospore discharged from the oophoridium of a Lycopod (SelagiTiella MerteTisii), 

 with the outer coat removed to show the young cellular prothallium, p, at the upper end. 

 Fig. 502. Vertical section of the prothallium and upper half of a large spore of a Lycopod 

 (SrlajjineUa dentvadatd). There are several archegonia, and in one of them, at a, there is a 

 central free cell, whence the leafy frond ultimately proceeds. Fig. 603. Vertical section 

 of a small portion of the prothalliiun and upper part of the large spore of a Lycopod (Sda- 

 ginella dentieidata), showing the embryo, e, developed from a central cell of one of the 

 archegonia, a, carried down by the growth of the suspensor, so as to be imbedded in the 

 cellular tissue at the upper part of the spore. 



