40 



VASCULAR CRYPTOGAMS 



as the ventral canal-cell, and the protoplasm of the larger and lower 

 portion rounds itself off into the oosphere. The two canal-cells then 

 deliquesce into mucilage, leaving an open passage for the entrance of 

 the antherozoids. 



The microspores, spherical orange or bright red bodies, remain in 

 a dormant condition through the winter, and undergo further develop- 

 ment in the spring. The contents then divide, first of all by a trans- 

 verse wall of cellulose near one end into two cells of very unequal size. 

 The smaller one of these does not divide further, and remains sterile ; 

 it is regarded as the last degraded vestige of a male prothallium. The 

 contents of the larger of the two cells, which may be regarded as an 

 antherid, then break up into from four to eight primordial cells, and 

 each of these divides again into four mother-cells of antherozoids ; but 

 it is uncertain whether all the cells are fertile. The antherozoids are 

 coiled up into a helix, and are furnished at the anterior end with two 

 long fine cilia. The antherozoid is in all cases derived from the nucleus 

 of the mother-cell ; a central vacuole, invested with a delicate membrane, 

 often remains attached to its posterior end during ' sw^arming.' The 

 ' swarming ' condition continues for about half to three-quarters of an 

 hour. 



^ 



M 6 



Fig. 21. — Formation of embryo and suspensor in 5. Martensii, showing order of formation 



of dividing walls. (After Pfeffer.) 



In the formation of the embryo the first division of the oosperm 

 differs from that in Rhizocarpese and in Fihces in taking place at right 

 angles to the axis of the archegone. It is thus divided into two super- 

 posed halves, from the lower of which is developed the embryo itself ; 

 from the upper half a structure almost pecuhar to this order, consisting 



