Holloway. — Prothallus, &c, of Tmesipteris. 



391 



Some additional figures illustrating the development of the sexual organs 

 are given in the present paper. That of the antheridium is easily followed 

 (figs. 9 to 19). It begins at an early stage to project from the surface, 

 and at the mature stage does so very strongly. The number of sperm- 

 cells is much less than in either Lycopodium or in the Ophioglossaceae. 



Fig. 7. — Longitudinal section of a stout apex of a prothallus, 



showing the apical cell. X 100. 

 Fig. 8. — Transverse section of a stout apex of a prothallus, showing 



the apical cell. X 100. 

 Figs. 9-17. — Developmental series of antheridia in longitudinal 

 section. X 100. 



Spermatogenesis was not followed, but Lawson states that the spermato- 

 zoids of Psilottim are multiciliate (12, p. 105). Two additional figures 

 illustrating the development of the archegonium are also given (figs. 20, 21). 

 It is clear that there is here no basal cell. The demonstration of neck- 

 eanal cells and the ventral-canal cell which was left over from my previous 



