FRESH-WATER ALG^ OF THE UNITED STATES. 201 



sexual part, does not, however, rupture the old wall of the mother-cell, but grows 

 out beyond it, and there dilates. The new cell is therefore divisible into two parts, 

 a proximal cylindrical portion, contained within the walls of the mother-cell, and 

 a distal more or less globular piece beyond the latter. The chlorophyllous proto- 

 plasm now collects in this dilated portion, leaving the basal cylindrical part bare and 

 empty. The oogonium is not, however, formed directly from this upper portion 

 (the primitive oogonium, as it may be called), but a new wall forms within the latter 

 and then it undergoes division much as did the primary cell. In this way it is that 

 the upper and lower portions of the old wall, i. e. that of the primitive oogonium, 

 remain as a sort of basal sheath and cap to the fully-formed sporangium. The 

 little hole by which the spermatozoids find entrance to the contents- of the oogo- 

 nium is always formed in the upper half of the wall of the latter. 



As stated, all the species of Bulbochoetece as yet known are gynandrous. The 

 antheridia resemble those of similar CEJdogoniecs, and their life-history is very similar. 

 The development of the resting spores is s.aid to take place as follows : The first 

 change is in the color of the spore, the bright red becoming green, especially near 

 the margins of the cavity. The outer wall is then ruptured and the spore grows 

 into a long oval body, whose contents are chiefly green with a sprinkling of the 

 original red. The protoplasm of this oval body gradually divides into four masses, 

 which become more and more distinct, until they are at last well formed zoospores, 

 similar to those produced in the more ordinary method, except, perhaps, that they 

 are redder. They are finally set free in the water by a solution of the cell wall 

 surrounding them, and enter upon a brief free existence, to settle down after a 

 little and grow into a fully-formed plant. 



Genus BULBOCHtETE. 



Androsporae in planta feminea. ortse, postea hane affixse etin antheridiis se formantes. 

 Androspore arising in the female plant, afterwards affixed to it and developing into the antheridia. 



B. ignota, Wood. 



B. sparse ramosa, elongata; articulis diametro max. (^\^" =^ .00011") 1^-3 plo longiori bus; 

 cogoniis long. ^^V = .0025", lat. ^^^/ = .0018", interdum lateralibus et sessilibus, inter- 

 dum inter ramulorum cellulas vegetativas positis, dissepimento nuUo ; oosporis ovalibus, longi- 

 tudinaliter nonnihil oblique et distante costatis, in ajtate provecta aurantiaco-brunneis, sporo- 

 dermate crasso ; antheridiis 3-4 cellularibus, stipitatis. 



Syn.—B. ignota, Wood, Prodromus, Proc. Amer. Pbilos. Soc., 1869. 



Hob. — In aquis quietis, prope Philadelphia. 



B. sparsely branched, elongate with the joints 1^-3 times longer than broad (y^Vir" = -OOOTr') ; 

 oosporangia .0025" long by .0018" broad, sometimes lateral and sessile, sometimes placed 

 upon the apex of a branch, sometimes situated in the length of tlie branches between their 

 cells; the empty cell which supports the sporangium without dissepiment; oospores, oval, 

 filling rather closely the cavity of the spore-case, longitudinally somewhat obliquely and dis- 

 • tantly costate, when mature orange brown ; spore-coat rather thiols ; antheridia 3-4 celled, 

 scarcely stipitate. 



Remarks.- When I described and figured this species I had never seen the 

 mature fruit, but very recently Mr. Quimby has communicated specimens to me. 



26 September, 1872. 



