176 FllESlI-WATER ALGJE OF TKE UKITED STATES. 



Syn.—Dotrydmm- arrjillaccum, Wallroth. Babenhorst, Flora Europ. Algarum, Sect. III. 

 p. 205. 

 Hydrogastrum granulatum, (Linn^us) Desv. Rabenhorst, loc. cit. 



Hah. Delaware ; (Dr. Billings) Wood ; West Point, New York ; Providence and Newport, 



Rhode Island ; Bailey. 



Mostly gregarious, often aggregate, not rarely confluent; cells pyriform, of the size of a poiipy 

 or mustard seed and larger ; pea-green ; surface pulverulent. 



Hemarks.— The above description is taken from Rabenhorst's work, and applies 

 to tlie specimens collected by Dr. Billings in the State of Delaware, excepting that 

 I did not discover any of them to be confluent, nor was their surface distinctly 

 pulverulent. Prof. Kiitzing gives as a comparative character between this and E. 

 Wallroildi, the smaller size of the spores; but Prof. E.. says nothing about this. 

 There were no spores in any of the American specimens, and I think it somewhat 

 uncertain whether or not the plant is or is not either of the European species. It 

 is very probable that it will be discovered that the only true specific characters are 

 sexual, and consequently have not as yet been made out in any of the forms. 

 Certainly the descriptions of the species as at present given seem to me not to 

 contain any reliable characters. 



Fig. 2 a, pi. 16, represents a very young state of our American plant; fig. 2 is 

 the perfected frond, both magnified ninety diameters ; fig. 2 a shows what is sup- 

 posably a perfected resting spore magnified 160 diameters. 



Family VAUCHERIACE^. 



AlgfD monoicse, cocspitosa?, unicellularcs. Cellula vegetiva (tliallus) vegetatione terminal!, ntriculi 

 formi-elongata et ampliata, promincntiis plus minus elongatis ramosa. 



Propagatio aut sexualis, fit oosporis ope spermatozoidiorum fecundatis, aut non sesualis zoogonidiis. 

 Fructificatio triplex (melius organa fructificationis tria) : — 



1. Sporangium terminale, ex tlialli apice plerumque globoso-clavato-tumido formatura, septo dis- 

 cretum, cytioplasmate obscure viridi, demum in zoogonidium (zoosporam, Thur.) unicum permag- 

 num, ciliis vibratoriis dense obsitum abeunte farctum. 



2. Oogonium (oosporangium) laterale, sessile vel prominentia, plus minus elongata vel simplici 

 vcl partita pedicellatum, cytioplasmate aetate provecta in oosporam singulam transmutato fetum. 



3. Antheridium laterale, sessile vel e ramuli lateralis parte suprema septo discreta formatum, in 

 quo spermatozoidea (antherozoidea, Thur.) numeros issima nascuntur, denique erumpunt. Sperma- 

 tozoidea oblonga, ciliis duobus inajquilongis, subpolo antico ortis instructa. (B.) 



Monajcious alga;, caspitoso, unicellular. Vegetative cells (thallus) growing'at the ends, elongate, 

 utriculiform, and ampliate, more or less profusely branched. 



Propogation either sexual, with oospores which are fecundated by spermatozoids, or non-sexual, 

 by means of zoospores. Organs of fructification of three kinds :— 



1. Sporangia, which are terminal and mostly formed from the separation of clavately swollen, 

 globose apex of the thallus (often of a branch) by means of a partition ; in the sporangium arises 

 a single, very large zoospore, which is densely clothed with cilia. 



2. Oogonia (oosporangia), lateral, sessile or pedicelate simple bodies, whose eytioplasm is finally 

 converted into an oospore. 



3. Antheridium lateral, sessile, or formed out of the end of a branch ; the spermatozoids formed 

 in them oblong, furnished with two unequal cilia, arising near the front end. 



