— 104 — 



able to give an indication where we should seek the conditions in 

 question. Probably the forms with main-trunks especially are 

 developed on fixed substratum in shallow water, where great 

 movement of the waves prevails, while the other forms occur in 

 more or less quiet water or as epiphytes on living often flexible 

 substratum. Thus I observed at Hellebæk on the north-east coast 

 of Sealand that the forma typica of C. diaphanum mostly occurred 

 in shallow water on stones, while the forma modificata was more 

 common in deeper water. As to the forma penicillata of C. fruti- 

 culosum Kütz. the Danish specimens are all collected on the North 

 Sea coast of Jutland on stones and piers near land. A typical 

 dichotomous specimen of this species (forma dichotoma), dredged in 

 deeper water is represented together with forma penicillata in plate 

 I (fig. 1 and 4). Intermediate forms also occur in shallow water 

 (e. gr. in the port of Frederikshavn) but no doubt always under 

 quiet conditions. The special form with main axes of C. rubrum 

 is forma secundata. The Danish specimens are all collected in the 

 North Sea on the coast of Jutland near land on stones and piers 

 in localities exposed to great movements of the waves. On the 

 coasts of the Færoes, where this form is very common in the 

 littoral and sublittoral Gorallina zone (Børgesen 1908, p. 751) it 

 occurs according to the verbal statement of Dr. Børgesen most 

 often on exposed coast and fastened to Corallina, Laminaria-stipes 

 and fixed substratum. Mr. Kylin states (1910, p. 36) that this form 

 on the coast of Norway occurs partly epiphytic partly on stones 

 and rocks. 



In my paper (1908) I describe a forma irregularis common in 

 the Kattegat and more to the southward. This form is inter alia 

 characterized by the dichotomous ramification. Certainly this form 

 is to be divided into two subforms, viz. a more dichotomous, and 

 a form with development of main-axes occurring in more shallow 

 and moved (?) water than the first. Such a forma irregularis from 

 shallow water I have reprensented in Plate III, fig. 17. 



List of the literature. 



Agardh, J. G., 1851: Species genera et ordines algarum, Vol. II, p. 1. 

 Borge s en, F., 1908: The Algae- Vegetation of the Færoese Coasts with remarks 

 on the Phytogeography ; Botany of the Færoes, Vol. III. 



