F. Børgesen; List of species. 475 



more robust, having much shorter and broader segments than 

 those of the vegetative branchlets in the same plant. The ripe 

 cystocarps are frequently placed in the upper end of the branch- 

 lets (comp. Fig. 431 a), but not always. Often the branch- 

 lets, bearing the cystocarp, get renewed gro\\i:h, attaining a 

 considerable length and in this way giving rise to a new branch- 

 let (comp. Fig. 431 a), these being composed of about the same 

 number of segments as the common branchlets and in their 

 upper end terminated by trichoblasts. 



And this development may be carried on still further. I have 

 found several specimens in which the branchlet growing out below 

 the cystocarp gets indefinite growi:,h hke the main filaments; 

 branchlets grow out from its dorsal side and it may develop 

 into a normally built main axis (Fig. 431 b). While in my 

 specimens the above mentioned three different cases occurred, 

 Falkenberg in his specimens has only found one form: a branch- 

 let growing out below the cystocarp. Falkenberg accounts 

 for this peculiar phenomenon by the increased supply of nutri- 

 tion to the cystocarps, which also benefits the branchlets and 

 favours the growth. 



The cystocarps are urceolate with a rather long neck and a 

 wide opening; they are about 300 // broad and 400 /^ long. 



The plant was found with cystocarps in the month of January. 



A slender form with tetraspores (Fig. 431 c) was once dredged 

 in deep water. The branchlets in this form are very long; at their 

 base about six sterile segments were present followed by one to 

 six fructiferous segments and finally a long sterile upper end 

 composed of about twenty long, but slender segments tapering 

 slowly upwards. The ramification of this plant was the same as 

 the cystocarpic plants, mentioned above. 



This plant was found at a depth of about 30 meters in the 

 month of March in the sound between St. Jan and St. Thomas: 

 off Cruz Bay. 



136. Dipterosiphonia dendritica (Ag.) Falkenb. 



137. Lophosiphonia obscura (Ag.) Falkenb. 



138. Lophosiphonia cristata Falkenb. 



In my previous examination of this plant I had only sterile 

 material at my disposal, now I have come across specimens with 

 cystocarps and tetraspores. 



