A Monograph of the Genus Alaria 31 



stromatic blade. A sort of segmentation, as it were, can be seen 

 in these stages (Plate XIX, fig. 9). Each segment indicates that 

 the cells in it are derived from the same mother cell, as an aréole 

 of the epidermal cells in an embryonal blade of Laminariaceaß.^) 



While these processes are going on, the apical cell of the 

 confervoid body remains single, but elongates npwards, keeping 

 the initial diameter. As soon as the linear, monostromatic blade 

 has been formed, the elongated apical cell begins to divide by 

 transverse septa and the resnlting filament qniclvly gains its length 

 by basipetal growth (Plate XIX, fig. 8, 9). It shows all the 

 characters of the hairs pecuhar to the Phseophycese. Something 

 quite similar was observed by Keinke^) in the sporelings of Scyto- 

 siplion pijgmœiis. From the uppermost marginal cell of each seg- 

 ment there starts a similar hair. Plate XIX, fig. 10 shows a 

 marginal part of a blade of about 3 mm. in length. In it, hairs 

 at various stages of development are found in considerable number, 

 but not in tufts. They are thicker than the primary hair at the 

 apex of the blade but undoubtedly are of the same nature. The 

 tufts of hairs on the surface of the blade, mentioned in describing 

 the species, come out in a much later stage. 



A filament resembhng the apical hair of the treated plant is 

 dehneated by Thueet^) for the sporelings of Stilophora rlikoides J. 

 Ag. It is to be remembered that the species is characterized by 

 having a single persistent hair at the apex of the frond. 



Summing up the results hitherto obtained from the observa- 

 tions on the adnlt forms of the Phœophyccse, we may distinguish 

 the modes of occurrence of the hairs and their relative positions 



1) Yendo : Development of Cost iria, etc., Tl. LIV, fig. 19. 



2) See Engleb und Pkantl : Pflanzenfamih'en, Algae, fig. 139 , c. 



3) Thuket: Zoospores des Algues, PI. 28, fig. 9. 



