i i: i: > n . w A T E ii ALGA: OF THE UNITED STATES. 55 



Light bluiHh-grcen, or olivaceous-green, apex in the mature filament prolonged into a long, 

 distinctly articulated hvulinc .-eta ; sheath trun-|>:tr< m in the immature filament distallr, 

 broad, and distinct although hyaline, below rather thick and elo.se ; in the mature filament 

 In-low close, indistinct, above dissolved in librilhu and wanting at the apex; beterocysU 

 globose, sometimes geminate. 



I '' marks. This plant was found growing with other low algae in a thick jelly, 

 whirh clothed some wet, dripping rocks near Manaumk. In tin- young filaments 

 the sheath is produced above into a broad, thick, gelatinous-looking portion, the 

 cavity of which is often scarcely apparent. The < ytioplusm in such filaments is 

 mostly of a li^ r ht hluish-grecn color, is granular and not very apparent. In older 

 filaments, the trichoina aho\e is pn. longed into a long, curved hyaline point, and the 

 sheath ju>t below the base of this is split into a number of fibrilla?. No spores 

 were perceived. Tlie increase of the species appears to take place in the follow- 

 ing manner: Near the middle of the filament a tumid swelling forms, in the 

 centre of which appears after awhile a constriction, and this increases until at last 

 there are shaped out the liavs of two filaments. Then the heterocysts appear, and 

 finally the two halves of the original trichoma separate each a perfect filament. 

 '>, pi. ").) Sometimes, instead of a pair of filaments being thus formed, but 

 a Millie base is shaped out at the place of swelling, and the original filaments split, 

 as it were, thus gi\ing origin to a second trichoma, which for awhile appears as a 

 branch of the former, but is soon detached from it. In some specimens there arc 

 two heterocysts, unless the proximal of these, which is a light orange-clay color, 

 represents a spore. 



:$, pi. >, represents different forms of this species. 



FAMILY SCYTONEMACK/E. 



Trichomata nrticulata, sjrpe moniliformia vel Bubmoniliformia, vaginata, pscndoromosa, erllulis 



limataneis, ad pseudoramulorum basin, vel interstitialibus, pleromque pacbydermaticis instruetn. 



Vagina; e straits pluribus (ctsi non semper distinct!*) formitse, superficic leeves, corrugatse vel 



!>eraUe, crustata*, nonnmqaam stratis exterioribus in fibrillas discedcntibus, baud raro passim 



intumescentcs vel ocreataj. 



etatio non terminalis; cellalarum TegptatiTarnm divisio ad unam dircctionem, initlo in tricho- 

 matibus medio, postea in utroque fine sirpe alternans. Cellule litnitanc:e ad utrumque polum loccllo 

 lueido instrnctte. 



Propagatio gonidiis plcrumqnc exnUima gencratione ortis. Oonidia plcrumque nnmerosa seriata 

 e vagina se exserunt tumquc in singala seccdunt. (R.) 



Filaments equal, articulate, often moniliform or snbmoniliform, vaginate, pseudoramose, fnrnif<he<1 

 with hetcrocysts which are either interstitial or at the base of the branches, and are mostly thick- 

 walled. Sheaths formed of numerous strata (not always distinct), their surface smooth, corrugate, 

 or roughened, the exterior stratum sometimes breaking up into fibrille, not rarely intnmescent or 

 ochreate. 



.'elation not terminal ; division of the cells occurring in one direction, in the beginning in the 

 middle of the trichoma, afterwards often alternately at each end. Heterocysts furnished with a trans- 

 lucent spot at each end. 



Propagation mostly by gonidia arising from the last generation Oonidia mostly numerously 

 seriate, passing out of the sheaths and then separating one from the other. 



