IV 



THE JUNGERMANNIACE^ 



lOI 



the vesicle is small, but always present, and the cilia somewhat 

 longer than the body (Fig. 45, F). The stalk of the antheridium 

 is long and at maturity composed of two rows of cells. Before 

 the central cells of the antheridium are separated from the peri- 

 pheral ones, the stalk shows a division into two tiers of two 

 cells each (Fig. 44, B), but it is only the lower one that forms 

 the real stalk ; the other forms the base of the antheridium 

 itself. The cells of the wall have numerous chloroplasts, but 

 the great mass of colourless sperm cells within make the ripe 



• r 





 ; ^ ;.■' '■ '^ ^■■'  '■ ■.■■ 



Fig. 45. — Porella Bolanderi (Aust.)- A, B, Cross-sections of young antheridia, x6oo; C, longi- 

 tudinal section of nearly ripe antheridium, X loo ; D, ripe antheridium in the act of opening, 

 X50; E, F, spermatozoids, X 1200. 



antheridium look almost pure white. If one of these is brought 

 into water it soon opens in a very characteristic way. The 

 cells of the wall absorb water with great avidity, and finally 

 the upper part bursts open by a number of irregular lobes 

 which curl back so strongly that many of the marginal cells 

 become completely detached. The whole mass of sperm cells, 

 with the included spermatozoids, is forced out into the water, 

 and if they are perfectly mature, the spermatozoids are quickly 

 liberated and swim away (Fig. 45, D). 



The female plants are decidedly larger than the males, but 



