104 



VASCULAR CRYPTOGAMS 



ar 



on the greater or less supply of nutriment. The antherids make their 

 appearance about five weeks after germination, the archegones not till 

 much later. 



The antherids arise at the extremity or margin of the male prothallia. 

 They are first separated off as papillae by a tangential wall ; further 

 divisions then arise, by which they are divided into a large central cell 

 and a single layer of much smaller peripheral 'mantle-cells.' The 

 contents of the central cell then divide into the mother-cells of the 

 antherozoids. These escape, still enclosed in the delicate wall of the 

 ' special mother-cell,' by the separation from one another, through the 

 action of water, of the apical cells of the mantle-layer ; the expulsion often 



takes place with considerable force, 

 and is due to the swelling up of the 

 walls of the mother-cells; sometimes 

 they emerge still all united together 

 into a ball. The antherozoids are 

 much more numerous than in ferns ; 

 probably several hundreds are formed 

 in each antherid ; they are also 

 much larger, being the largest in any 

 class of Cryptogams. Each anthero- 

 zoid (see fig. 78) is a thread of pro- 

 toplasm, gradually narrowing from 

 the posterior to the anterior end, 

 where it is coiled spirally, and bears a 

 tuft of very long delicate vibratile 

 cilia. The posterior portion is 

 widened into a thin membranous 

 fin-like expansion, by the undula- 

 tions of which its motion through the water is greatly assisted, and may 

 continue for many hours. To the posterior portion of the antherozoid 

 is also frequently attached for a time a minute bladder containing 

 starch, which is regarded by some as the wall of the special mother-cell, 

 by others as a vesicle contained in it. The body of the antherozoid 

 appears to be formed from the nucleus of the mother-cell, its cilia from 

 the cell -protoplasm. 



The archegones are formed on the under (shaded) side of the thick 

 lobed portions of the female prothallia, a lobe being usually situated 

 immediately beneath an archegone, and assisting in its impregnation by 

 retaining water. By the continued growth of the subjacent tissue they 

 are ultimately pushed on to the upper surface, and hence the direction 

 of growth of the archegone is the opposite of that of ferns. Otherwise 



FIG. 80. Portion of female prothallium of E. 

 sylvaticum, with projecting archegone, ar. 

 (After Buchtien, greatly magnified.) 



