PH AOPHYCEA 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.”! 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 Adenocystis? (Laminariacer, p. 84), though it 
presents a contrast with the conceptacle of Splachni- 
diwm, which bears hairs only at first, and sporangia 
later on. Though not comparable with the more 
highly developed cryptostomata of the Fucacecw, 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 
1M. O. Mitchell, in Murray’s Phycoloyical Memoirs, part ii., 
p. 54. - 
2 Murray in Phyc. Mem., part ii., p. 62. 
