BRYOPI1YTES 101 



Thallophytes. Instead of being a single mother cell, it is 

 a many-celled structure, shaped like a flask (Figs. 83, 98). 

 The neck of the flask is more or less elongated, and within 

 the bulbous base (venter) the single egg is organized. The 

 archegonium, made up of neck and venter, consists mostly 

 of a single layer of cells. This hollow flask is solid at first, 

 there being a central vertical row of cells surrounded by 

 the single layer just referred to. All of the cells of this 

 axial row, except the lowest one, disorganize and leave a 

 passageway down through the neck. The lowest one of 

 the row, which lies in the venter of the archegonium, or- 

 ganizes the egg. In this way there is formed in the arche- 

 gonium an open passageway through the neck to the egg 

 lying in the venter. 



To this neck the swimming sperms are attracted, enter 

 and pass down it, one of them fuses with the egg, and this 

 act of fertilization results in an oospore. 



Archegonia and antheridia are supposed to have been 

 derived from a many-celled gametangium, such as occurs 

 in certain Brown AlgaB (Fig. 18). The presence of the 

 archegonia is one strong and unvarying distinction between 

 Thallophytes and Bryophytes. Pteridophytes also have 

 archegonia, and so characteristic an organ is it that Bryo- 

 phytes and Pteridophytes are spoken of together as Arclie- 

 goniates. 



65. Germination of the oospore. The oospore in Bryo- 

 phytes is not a resting spore, but germinates immediately 

 by cell division, forming the sporophyte embryo, which 

 presently develops into the mature sporophyte (Fig. 85, A}. 

 The lower part of the embryo develops the foot, which ob- 

 tains a firm anchorage in the gametophore by the latter 

 growing up around it (Fig. 85, B, C). The upper part of 

 the embryo develops the seta and capsule. As the embryo 

 increases in size, the venter of the archegonium grows also, 

 forming what is called the calyptra ; and in true Mosses 

 the embryo presently breaks loose the calyptra at its base 

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