CALIFORNIAN HOT SPRING. 253 



These larger threads are apparently produced from the 

 smaller filaments by a process of growth. 



Near the base and in the under portions of the fronds, 

 these filaments are scattered in the homogeneous jelly in 

 which they run infinitely diverse courses. In the upper por- 

 tions of the frond, and at some little distance from the base, 

 the adjoining cells are very close to one another, and pursue 

 more or less parallel courses, with enough firm jelly between 

 to unite them into a sort of membrane. 



This plant certainly belongs to the Nostochaceae, and seems 

 a sort of connecting link between the genera Hormosiphon 

 of Kiitzing and Nostoc. 



The best algologists now refuse to recognise the former 

 group as generically distinct ; and the characters presented 

 by this plant seem to corroborate that view. 



The species appears to be an undescribed one ; and I 

 would propose for it the specific name Caladarium, which is 

 suggested by its place of growth. There are several species 

 of allied genera, which grow in the hot springs of Euro]je ; 

 but no true Nostoc has, I believe, been found before in ther- 

 mal waters. The following is the technical description of 

 the species : 



N. caladarium, sp. nov. 



iV. thallo maximo, indefinite expanse, aut membranaceo- 

 coriaceo vel membranaceo-gelatinoso vel membranaceo, aut 

 Isete virdi vel sordide olivaceo-viridi vel olivaceo-brunneo, 

 irrcgulariter profundc laciniato-sinuato, ultimo eleganter 

 laciniato ; trichomatibus ina^qualibus, interdum flexuoso- 

 curvatis, j^lerumque subrectus et arete conjunctis, in formis 

 duabus occurentibus : forma altera parva, viridis, articulis 

 cylindricis, cum celkilis pcrdurantibus hie illic inteijectis, 

 vaginis interdum obsoletis, seepius diflfluentibus, instructa ; 

 forma altera maxima, articulis globosis vel oblongis, auran- 

 tiaco-brunneis, cellulis pcrdurantibus ab ceteris baud di- 

 versis. 



Diam. Cellulae cylindricee maximae , „ j,oo unc. ; cellulgc 

 perdurantis ^-oVo unc. 



Diam. Forma; primaj articuli maximi -tjtmTo i-^nc. ; cellida? 

 perdurantis -^-nVo unc. Forma) secunda; articuli longi -o^-^Vu 

 to WcTo unc, lati ^-^ to ^-Vu, articuli globosi -^^hu to Tinnr 

 unc. 



Adherent to, and often more or less imbedded in, the 

 fronds of the Nostoc, were scattered frustules of several 

 species of diatoms, none of which was I able to identify. 

 In some of the fronds there were numerous unicellular Alga% 

 all of them representatives of a single species belonging to 



