no MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



The Phaeo stroma grows associated with Elachistea stellulata, 

 Strehlonema solitariiim, Acrochaetium affine, etc. It seems to 

 prefer to border the closely repent stolons of the hydroid and it 

 sometimes covers the stolons themselves. Most of the plants 

 bear the unilocular sporangia; those with plurilocular sporangia 

 are rare. Some of the plants with unilocular sporangia seem to 

 show all gradations between the isolated scattered sessile sporangia 

 (Fig. 6) and those that are aggregated on an elevated submori- 

 form sorus (Fig. 9), and we believe that this variation in the mode 

 of occurrence of the sporangia has no particular morphological or 

 physiological significance. The elevated sori obser\'ed have been 

 few in number and we have not ventured to sacrifice them in an 

 attempt to make a vertical section through them, but we infer 

 that the sterile pseudoparenchyma forming the base of the sorus 

 is more than one cell thick. Elsewhere, the thallus is manifestly 

 unistratose. 



Of the four species that have been hitherto proposed for the 

 genus Phaeostroma the present plant seems most closely allied 

 to the type of the genus, P. pustulosum Kuckuck, which occurs 

 on the leaves of Zostera and on \'arious algae in northern Europe 

 and Greenland. From this, however, as figured and described 

 by Kuckuck,^ P. pusilliim appears to differ amply in the smaller 

 thallus, which remains unistratose in sterile parts, in the series 

 of very short cells at the bases of the hairs, in the more regular, 

 more ovoid, more ectocarpoid, less tuberiform, less aggregated 

 plurilocular sporangia, and in the smaller (5-16^1 vs. 25-40 /i) 

 unilocular sporangia, which sometimes occur in elevated sub- 

 moriform sori. So far as we are aware, the genus Phaeostroma 

 has not previously been reported from the American continent. 



Elachistea stellulata (Harv.) Griff.; Aresch. Linnaea 17: 261. 

 pi. g.f. 4. 1843. Harv. Phyc. Brit. 1: pi. 261. 1846-51. 

 Sauv. Jour, de Bot. 6: 6. pi. i.f. i, 2. 1892 

 Conferva stellulata Harv. Man. Brit. Alg. 132. 1841. 

 Phycophila stellulata Kiitz. Sp. Alg. 541. 1849. 

 Myriactis stellulata Batters, Jour. Bot. 30: 173, 174. 1892. 



On and in Dictyota dichotoma, "in 133^-14 fathoms" of water, 

 Lewis Radcliffe, August 11, 1914; associated with Streblonema 



1 Bot. Zcit. 53: 182-187. pi. 7. 1895. 



