84 l')iiv< rsit}/ of California Publications in Botany L^'o^-S 



1891, p. 926, and below, under Microcoleus). With the exception of 

 Porphijrosiphon, the genera referred to the subfamily Schizotricheae 

 consist of species whose individuals always show a fair proportion 

 of more than one trichome in a sheath. 



Key to the Genera. 



1. Trichomes few in a sheath 21. Hydrocoleum (p 84) 



2. Trichomes many in a sheath 22. Microcoleus (p 85) 



21. Hydrocoleum Knetz. 



Plant mass forming a compact, smooth or caespitose cushion on 

 the substratum, at times encrusted with lime ; filaments with hyaline, 

 cylindrical, sublamellate sheaths, sparingly false branched, more or 

 less mucous, at times completely diffluent; trichomes few and loosely 

 aggregated in a sheath, apices straight, more or less attenuate and 

 capitate, with terminal cell wall thickened. 



Kuetzing, Phyc. Gen., 1843, p. 196. 



It has seemed best to retain the original spelling of the name of 

 this genus, although, of late, it is being written " Hydrocoleus" (cf. 

 Forti, 1907, p. 315, and others). The assumption is, presumably, that 

 "Hydrocoleum" is an orthographic error. The change may also be 

 made to make it agree with Microcoleus. There seem to be two words 

 in Greek, or even three, meaning sheath, viz., 6 Ko\e6<i or to KoXeov, 

 the sheath or scabbard of a sword, and tokoXcov (alternative KovXeov) ^ 

 a sheath ; the two latter are Ionic forms to be sure, but no attempt 

 has been made to limit the choice of Greek, in derivatives, to the Attic 

 dialect alone. to koXcov, however, is Attic, so that it seems perfectly 

 proper to retain the name in the form in which Kuetzing wrote it, 

 since either "Hydrocoleum" or "Hydrocoleus" may be considered 

 orthographically correct. 



The genus Hydrocoleum was founded b}^ Kuetzing on two fresh 

 water species which he named H. ho'moetrichum and H. Keterotrichum, 

 respectively. The first, which may be considered properly as the type 

 of the genus, was found on stones in a small cataract near Trieste. 

 The second species was apparently founded on a mixture of H. homoe- 

 trichum and another species, for which the name has been retained by 

 Gomont. About twenty-eight species have been described as belonging 

 to this genus of which one quarter are marine. The species are to be 

 distinguished from those of Microcoleus and Sirocaleum, the only other 

 marine genera, by having the trichomes less numerous in the sheath. 



