68 



VASCULAR CRYPTOGAMS 



papilla divides first of all into a central cell surrounded by a single layer 

 of peripheral cells. These last are barren, but contain chlorophyll ; 

 while the central cell divides still further, each derivative nearly cubical 

 cell then producing a flat spirally-coiled antherozoid contained within a 

 vesicle, or * special parent-cell.' In no case is the number of anthero- 

 zoids produced by a single antherid very considerable. The function 

 of the peripheral cells appears to be to absorb water violently when the 

 antherid is mature, in consequence of which they swell up considerably 

 and rupture the central cells, thus causing the escape of the parent-cells 

 of the antherozoids. From each of these is then discharged, by the bursting 

 of its delicate cell-wall, an antherozoid consisting of a flat band of proto- 

 plasm coiled spirally three or four times, and bearing at its anterior end 



a number of fine 

 cilia (fig. 44). To 

 its posterior end is 

 frequently attached 

 for a time a vesicle 

 containing starch- 

 grains, which is pro- 

 bably the remains of 

 the special parent- 

 cell of the anthero- 

 zoid. AS in other 

 Vascular Crypto- 

 gams, the body of 

 the antherozoid ap- 

 pears to be formed 

 from the nucleus of 

 the mother-cell, the cilia from the cell-protoplasm. 



The archegones are produced on the under side of the cushion of the 

 pro thallium, but in much smaller numbers than the antherids. Like 

 them, each archegone is derived from a single superficial cell, which at 

 first bulges only slightly, and is first divided into three cells by two 

 tangential walls. The lowermost of these three, or basal cell, divides 

 further, and takes its share in the formation of the venter, or swollen 

 part of the archegone, which is altogether imbedded in the prothallium. 

 The outermost of the three cells develops into the neck-wall, or outer- 

 most wall of the neck of the archegone, dividing at first into four cells, 

 from which the four rows of cells which constitute the neck are formed 

 by oblique septa. Since the neck grows more rapidly on the anterior 

 side, i.e. the side nearest to the apex of the prothallium, and hence 

 becomes convex on that side, the number of cells is also larger in the 



FIG. 46. Archegone of Pteris serrnlata L. at the moment of the 

 expulsion of the mucilage ( x 350). (After Strasburger.) 



