43 



A. Without terminal sporangia. 



a. with incurved branches A. incurva. 



b. without incurved branches A. hystrix. 



B. With terminal sporangia A. j)enicilliforrnis. 



83. .4. incuFTa Kjellm., Acrosiphonia p. 61, Cladophora 

 (Spongomorpha) arcta a. typica and ß. pulvinata K. Uosenv. Grl. 

 Havalg. p. 907. 



The Greenlandic specimens are 

 2—6 cm. high and 130—170// thick. 

 The sporangia occur singly, two or 

 three together, or up to 7 in a row. 

 Incurved branches occur, but rather 

 rarely. The lower part of the main 

 axis of young plants terminates 

 in an axiJe rhizoid, which dies off, 

 as the plants grow older and the 

 number of lateral rhizoids increases; 

 in many cases it is replaced by a 

 new axile rhizoid of intra-matrical 

 origin, but usually the old specimens 

 show the lower end of the main 

 axis dying off. The lower end of 

 the rhizoids is generally consid- 

 erably enlarged, and often irregularly 

 branched; sometimes these branches 

 are well developed stolons, emitting 

 erect filaments. The rhizoids are as 

 a rule densely entangled below, as 

 the branches or lobes of the basal cells work into each other. 

 The apex of rhizoids not touching the substratum is not enlarged 

 but incurved or hooked, and may be considered as a kind of 

 prehensile organ. 



Injured rhizoids, the lower part of which is dying off or 

 has been thrown awav, are in manv cases renewed by an 



Fig. 4. Acrosiphonia incurva 



Kjellm. 

 A basal portion of a plant 

 showing the lower end of the 

 main axis dying off and lateral 

 rhizoids with their widened 

 and branched basal cells. To 

 the left a stolon emitting an 

 erect filament is to be seen. 

 25: 1. 



