MlCROSPORA 167 



On rock or earth in rapids of grassy meadow streams. 



Thomaston, Conn., May (568). 



This species has a superficial resemblance to 5. fluitans, but 

 differs from it in the strong tendency of the filaments to stability, 

 and in the much clearer green and clean-cut character of the 

 chromatophores, with their more distinct pyrenoid. The genic- 

 ulations in this species have a much more permanent character 

 than those of 5. fluitans ; there they appear to arise simply from 

 the excessive tendency to dissociation of the cells, while here they 

 arise from the irritation of cells as they are pressed upon the sub- 

 stratum by the current. The rhizoidal structures are here very 

 different from the basal cells in Ulothrix, their cell-walls are 

 thickened only in a slight degree, and the chromatophore retains 

 nearly its normal character ; there is every evidence that here 

 they are always developed secondarily as tendril-like organs, and 

 not at the germination of the zoospore as in Ulothrix. Zoospores 

 were not formed freely in our specimens, though some cells from 

 which they had emerged were found. 



There appears to be no sufficient raison d'etre for Wolle's var. 

 cataracta since the characters on which it is founded are mentioned 

 in Kiitzing's descriptions of the species. 



III. MlCROSPORA Thuret, Ann. Sci. Nat. Bot. III. 14: 221. 

 1850. Lagerh. Ber. Deutsch. Bot. Gesell. 5: 413-417. 1887. 

 Flora, 72 : 207-209. 1889. Not Microspora Hassall, Ann. 

 & Mag. Nat. Hist. 11 : 363. May, 1843 {^Cladophora Kiitz. 

 Linnaea, 17: 91. 1843).* 



Filaments simple, generally .unattached and with little differ- 

 ence between base and apex. Chromatophore a granular band or 

 sheet covering more or less completely the outer cell-wall and the 

 dissepiments, sometimes perforate or reticular, without pyrenoids 



* Hassall' s genus Microspora had for its type Conferva glomerata L. and would 

 supplant Kiitzing's Cladophora if it should be proved that HassalPs work was published 

 earlier in the year 1843 than Kiitzing's. Probably, however, Kiitzing's work in the 

 first Heft of Linnaea appeared earlier than May, the published date of Hassall' s paper. 

 Hassall ('45) himself abandoned his Microspora in favor of Kiitzing's Cladophora. 

 Since, therefore, Microspora Hassall is never likely to be taken up again, it has been 

 thought best to waive a too strict application of the article of the Rochester Code in 

 regard to homonyms and to retain the only Microspora that has ever been in general 

 use. 



