The Development of Costaria, Undaria, and Laminaria. 
BY 
K. YENDO, Rigaicuhakushi, 
Professor of Marine Botany , Imperial University, Sapporo. 
With Plates L1II-LV. 
UITE recently, Drew 1 has discussed the behaviour of the spores of 
Laminaria, and concluded that they are gametes and not zoospores. 
This diverges somewhat widely from the view hitherto held by eminent 
botanists for many years. Yet I hope his observation has revealed the truth, 
as there seem to occur in nature other cases which may be more easily 
explained by granting the fusion of two spores of Laminariaceae. For 
instance, Hirome undarioides , Yendo, stands as an intermediate form between 
Undaria pinnatifida , Sur., and Laminaria radicosa , Kjellm., in its habit, 
texture, and propagating organs. An explanation of the genetic relation¬ 
ships between them may be facilitated if hybrids of Laminariaceous species 
have been proved possible. 
Whatever the spores in the sori of Laminariaceae maybe, and whatever 
sort of evolution takes place during germination, ‘the full development from 
spore to adult has not yet been studied for any member of the Laminariaceae.’ 2 
Thuret 3 briefly described and beautifully figured some embryonal stages of 
Saccorhiza bnlbosa some sixty years ago ; and this is the only direct evidence 
we have with reference to the sporelings of the Laminariaceae. Barber, 
Setchell, Reinke, Foslie, McMillan, Griggs, and others who have traced the 
stages of development in various members of the Laminariaceae have started 
from much later stages than Thuret described. Among these authors 
Setchell gives the most important account as regards the details concerning 
the development of the internal structure. As the result of the studies of 
these botanists we are led to believe, though without exact evidence on many 
particular points, that most members of the Laminariaceae are simply rows 
of cells at the beginning ; that they then become monostromatic, and add the 
new layers of cells at the lower middle part of the lamina ; that the simple 
1 Drew : Reproduction and Early Development of Laminaria digitata and L. saccharina. Ann. 
of Bot., xxiv, No. 93, 1910. 
2 Setchell: Post-embryonal Stages of the Laminariaceae. Univ. of Cal. Public., vol. ii, No. 4, 
1905. 
3 Thuret: Recherches sur les Zoospores des Algues. Ann. des Sci. Nat., Bot., 1850. 
[Annals of Botany, Vol. XXV. No. XCIX. July, 1911.] 
