122 



THE AMERICAN MONTHLY 



['h^]y, 



ferent forms of the vegetative cells, 

 the different modes of fruiting, and 

 the different positions and charac- 

 ters of the oogoniums. 



The plants of this genus belong 

 to the higher, sexual grade of 

 plant development. The mother 

 cell (o()gonium) contains a single 

 embryo (oospore). The develop- 

 ment of fertilizing germs consti- 

 tutes a feature not observable in 

 the lower forms. Certain cells of 

 the filaments produce these gei-ms ; 

 they are called Zicerg Mdnchen by 

 the Germans ; technically J^an- 

 naners, signifying dwarf men ; they 

 are the antheridia. The cells in 

 which they are developed are the 

 androsporangia or spermatogonia. 

 The dwarfs escape through a slit in 

 the side of a cell, or by the sepa- 

 ration of two cells, and find their 

 way to the mother cell when it is 

 partially developed, and lodge on 

 it, or on a cell immediately above 

 or below it. The oogonium (mother 

 cell) contains the embryo of the 

 plant ; when in condition for fruc- 

 titication, a small pore opens on the 

 side or upper end of the mother 

 cell, and through it are injected 

 the spermatozoids which are de- 

 veloped in, and ejected by the 

 dwarfs. The oospore, lodged in 

 the oogonium, is thus fructified. 

 It lies dormant for a season after ma- 

 turity,but finally leaves the mother 

 cell and reproduces the original form. 



There is another process of de- 

 velopment denominated the asexual 

 process. This is shown in Fig. lY, 

 representing a specimen found in a 

 pond near Hammonton, N. J. 

 Thousands of these plants were 

 growing on twigs and rootlets. I 

 found no evidence of sexual propa- 

 gation, but the filaments were well 

 supplied with oval cells, attached 

 at the joints, not unlike the o5gonia 

 in other forms. These open at the 

 top by a lid (operculum) which is 



thrown back by an upward pres- 

 sure from within ; then follows an 

 interesting process, the young (zo- 

 ospores) slowly working their way 

 out like little chicks escaping from 

 the e^gs; the illustration shows 

 these immature forms in various 

 stages and positions of the process 

 of ejectment. 



A similar feature of development 

 is often observed in a sister family, 

 the QEdogoniums, but in these the 

 zor)spores come out from the vege- 

 tative cells of the filaments, not 

 from distinct cells. 



These young Bulbochsete forms 

 (zoospores?) do not appear to be 

 provided with celia ; they evidence 

 none of the activity common to 

 zoospores. The two or three prongs, 

 pseudo-rootlets, are formed before 

 the young come out of the matri- 

 cular cell, a feature which is also 

 distinct from the zoospores of the 

 ffidogoniums. These young forms 

 find a place where to attach them- 

 selves and then grow. The seta 

 appears first on the rounded end of 

 the cells ; then the apex to which it 

 is attached separates, and cell walls 

 are formed. This process is repeated 

 many times until the larger plants 

 are developed. The seta which was 

 the end of the first cell, is now the 

 seta on the end of the filament. 



Fig. I represents JB. rectangu- 

 laris Wittr., from Wayne Co., Pa. 

 Fig. IV is B. intermedia^ De Bar., 

 frequent in our ponds. Fig. Ill, 

 species not determinable for lack 

 fruit ; from pond in New Jersey. 

 Fig. V, B. y?a/i«, Wittr., not unfre- 

 quent. Fig. II, B. trdrabilis, 

 Wittr., a variety, pond, New Jersey. 



o 



Finishing Slides. 



Having used damar dissolved in 

 benzole as a mounting medium for 

 some time past, I find that when 

 thoroughly dry, the gum becomes 

 brittle, and a sliglit jar is apt to 



