107 



formation of these hairs, the cells immediately sur- 

 rounding them undergo similar changes, and thus 

 the cryptostoma enlarges radially. Meanwhile the 

 thallus continues its growth, so that the basal cells of 

 the hairs which were originally in the same plane as 

 the epidermis have now come to lie below it, and the 

 whole structure is suggestive of a conceptacle." L It 

 is interesting to note that the formation of a crypto- 

 stoma is the starting point for the formation of a sorus 

 of plurilocular sporangia from the adjacent epidermal 

 cells. This spreads radially from the cryptostoma as 

 from a centre, and the formation of sporangia is suc- 

 ceeded, after these have disappeared, by that of club- 

 shaped paraphyses from the basal cells that bore the 

 sporangia. While the basal cells nearest the crypto- 

 stoma are producing paraphyses, those farthest away 

 are still giving rise to sporangia. Gradually the 

 paraphyses replace the sporangia until the latter 

 disappear, and there is left a group of paraphyses 

 with a central cryptostoma. This occurrence of a 

 central cryptostoma in the sorus recalls the case 

 of Adcnocystis 2 (Laminaricicccv, p. 84), though it 

 presents a contrast with the conceptacle of Splachni- 

 dium, which bears hairs only at first, and sporangia 

 later on. Though not comparable with the more 

 highly developed cryptostomata of the Fucacccc, we 

 have here an elementary form of cryptostoma, and it 

 is instructive to observe that the development of 

 cryptostoma and sorus originates in the alteration of 



1 M. O. Mitchell, in Murray's Phycoloyical Memoirs, part ii., 

 p. 54. 



2 Murray in Fhyc. Mem., part ii., p. 62. 



