Development of Laminaria bulbosa , Lamour. 55 
appear to be any mention of nuclei in the works of Reinke, Dodel-Port, Wille, 
Will, Humphrey, and Grabendorfer ; and the exquisite drawings of Riocreux in 
Thuret’s Notes Algologiques are unfortunately not distinct on the point. I have 
no doubt that in the Phaeophyceae, as in the Rhodophyceae, the greatest variation 
in this respect occurs. In the latter division of Algae the greatest diversity prevails. 
Thus, according to Schmitz, of different species of Callithamnion, some have only uni- 
nucleate cells {C. plumula, etc.) ; in others the young cells have single nuclei, but 
when they increase in size the cells have several nuclei ( C . granulatum, etc.) ; 
finally, in other species, the youngest cells of the growing apex have several nuclei 
(jC. Borreri , etc.) \ The number of nuclei present in the cells of these plants seems 
then to be of no systematic value ; there is, however, such a marked uniformity in 
some groups (Siphoneae) that the character may become of importance in this 
respect. I regard it as very probable that multinucleate cells will be found in 
many of the larger brown seaweeds ; and they might be especially sought for in the 
cells of the hyphal tissue. 
It has been stated that at the formation of the ridge there 
is no appearance of special activity in the epidermal cell- 
division at this point. At the very earliest indication of a 
swelling round the stalk there is, however, a marked change 
in the arrangement of the cells of the pith and cortex. The 
cells of these parts, and especially such as form the boundary 
line between them, become much larger than the rest. The 
elongation takes place in a direction curving obliquely out- 
wards towards the epidermis ; and the appearance suggests 
that these cells become elongated and push the external cells 
outward before them. Here, as in other parts, the increase 
in thickness of the stalk is due rather to the growth of the 
cells than to their increase in number. There is, accompany- 
ing this enlargement of the cells, a great development of their 
walls, and an early formation of the hyphal tissue ; so that in 
this respect, also, the manner of growth appears to be the 
same at the ridge as it is in other parts. 
As already mentioned, the growth above differs from that 
below the ridge. It is not easy to compare the thickness of 
these parts at different ages, because the part of the stalk 
above the ridge immediately assumes a flattened form (Fig. 2), 
while the primary fixing portion retains its circular, transverse 
section. There appears to be an entire absence of the hyphal 
Verh. d. naturh.Ver. Bonn, 1880, p. 125. 
