11 



only 8/^ thick. The ramification is alternate, in the upper part 

 subdichotomous. 



Hairs as a rule are absent; only a few times have I found 

 the apices of the branches provided with hairs (Fig. 5 5); these 

 were 3u broad. The chroniatophore consists of thread-like, sinuate 

 plates (Fig, 5D, F). In each cell one nucleus is present (Fig. 5£', F). 



The plant is not corticated. 



The sporangia are obovate-oblong, tetrahedrally divided (Fig. 5 

 C, D); they are sessile and occur on the uppermost and inward 

 side of the mother-cell. They are found in special individuals, but 

 a few scattered tetrasporangia can also occur in the female plants 

 (Fig. 6). The tetrasporangia are 

 about 40// long and 27;^ broad. 



The antheridia (Fig. 5£', F) 

 are found at the same places as 

 the tetrasporangia; they consist 

 of a system of closely placed, 

 short branches, of which each 

 bears 2—4 spermatia mother- 

 cells. The cystocarps (Fig. 5 G 

 and Fig. 6) are binate and trilo- 

 bed heart-shaped, sometimes also 

 more irregularly formed. The 

 younger and smaller ones only 

 consist of a single layer of carpo- 

 spores (Fig. 57:C), but in the bigger 

 cystocarps and especially in the 

 more irregularly shaped several 

 layers are also present. 



The carpogonic branch is four- celled and possesses a very long 

 trichogyne (Fig. 5/). 



The plant occurred as a common epiphyte on Gracilaria Blodgetti 

 in deeper water (ca. 15 fathoms) in the sound between St. Thomas 

 and St. Jan: off Cruzbay. It was found with tetraspores, antheridia 

 and cystocarps in the month of March. 



Callithamniou byssoides Arn. 



Arnott in Hooker's Brit. Flora, Vol. II, p. 342. 

 The specimens I have referred to this species were distinguished 

 by having irregularly lobed cystocarps. They were very like a 



Fig. 6. Callithamnion cordatum nov. sp. 



Branch with cystocarps and a single tetra- 

 sporangium (50 : 1). 



