50 



MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



The trichomes of Hydrocoleum are attenuated and capitate, as 

 diagnosed by Gomont. In his original diagnosis of the genus 

 Hypheotlirix, Kuetzing {loc. cit., 229) does not mention the char- 

 acter of the apices of the trichomes. The presence of two or 

 more trichomes within a sheath according to Kirchner' led 

 Gomont to reduce the genus to a subgenus of ScJiizothrix. But 

 neither in his original description (Essai, 352. 1890) nor in 

 his second publication of the subgenus" did he mention the char- 

 acter of the apices of the trichomes. Forti, in De Toni (Syll. 

 Alg. 5: 315. 1907), restores the subgenus to generic rank and 

 emends it so as to include only those species with trichomes hav- 

 ing straight, attenuated, and capitate .apices. Accepting this 

 limitation (purely arbitrary) of the genus would exclude the 

 material under discussion from Hijpheothrix, on account of its 

 very acute apices. The only real distinction between the two 

 genera, Hypheothrix and Hydrocoleum, as diagnosed by Forti 

 {loc. cit.), seems to be that in the former the trichomes are not 

 capitate and in the latter they are. The Porto Rican material 

 conforms to the former in this, as well as in other characters, 

 and I am placing it there as a very distinct species of the genus. 

 The only species of the forty-three which Forti recognizes which 

 approximates to it is HypheotJirix pallida (Naeg.) Kuetz. It dif- 

 fers from that species in the absence of an ample lamellose 

 sheath, as well as in other minor details. 



Hypheothrix longiarticulata sp. nov. 

 Plate 10, figure 95 



Filaments prostrate, scattered among other Myxophyceae, 

 4.5-5.5 M diam., moderately regular and smooth along the sur- 

 face, more or less branched near the ends; trichomes mostly 

 single, occasionally two in a sheath, 1.7-2 \x diam., not con- 

 stricted ; cells 8-12.5 n long, homogeneous ; apical cell conical ; 

 sheath homogeneous, white. 



Growing on a wall in Fort San Cristobal, San Juan, no. 

 2022 a, type. 



Hypheothrix parciramosa sp. nov. 



Plate 10, figure 9G 



Filaments loosely adhering into erect, subparallel, spinulose 

 fascicles 3^ mm. high, branched near the base, producing long, 



sEiigler & Prantl, Naturl. Pflanzenfam. li^: 07. 1S98. 

 10 Ann. Sci. Nat. Bot. VII. 15: 306. 1892. 



