232 



Dansk Botanisk Arkiv, Bd. 3. Nr. 1. 



other hand, are much less developed; they are here present as 

 quite thin ribbons with a great distance between them. 



If we now compare these small, but robust 

 specimens with the ones occurring in deep 

 water, we shall find the habit of the plant 

 much altered. The plant is much larger 

 often 2 — 3 cm. high, but, on the other hand, 

 much more slender and weakly developed. 

 All parts of the plants are more or less 

 elongated, the cells of the central filaments 

 being longer, but less broad and having 

 thinner walls. The same holds good with 

 regard to the branchlets, these being, on the 

 whole, less developed, shorter, and not form- 

 ing such a dense cover round the axis as 

 they did in most cases in the plants from 

 exposed places. 



As to the reproductory organs I 

 only found tetraspores and antheridia. 

 The tetrasporangia issue from the 

 cell in the branchlets (Fig. 221); they 

 cruciately divided. 



The antheridia are developed quite in the 

 same w-ay as described for Crouania Schousboei Thur. by Bornet 

 and Thuret in Notes algologiques (p. 185, pi. 49, fig. 5). The peri- 

 pheric cells of the branchlets are repeatedly dichotomously ramified, 

 and the uppermost ones of the small 

 cells, resulting from these divisions, are 

 the antheridia. 



The plant has been found with 

 tetraspores and antheridia in the months 

 of Jan. — March. 



As mentioned above it occurs as 

 well in shallow water as in deeper ; when 

 growing in shallow water it is often found 

 in rather exposed places where it is 

 dashed constantly by the waves ; in such places it often occurs as 

 an epiphyte upon Amphiroa fragilissima. In deep water I have 

 only collected it once at a depth of about 20 meters ; it was here 

 fastened to Caulerpa crassifolia. 



Crouania attenuata seems to be a common species along the shores of 

 the Islands. 



Fig. 220. Crouania 

 attenuata (Bonnern.) 

 J. Ag. Rhizoid grow- 

 ing out from the basal 

 cell of a branchlet. 

 (About 120:1). 



have 



basal 

 are 



Fig. 221. Crouania attenu- 

 ata (Bonnern.) J. Ag. Bases 

 of branchlets with young 

 tetrasporangia. (About 

 400:1). 



