FRESn-WATER ALG^ OF THE UNITED STATES. 1<)7 



A. rarely sctigcrous ; articles 2-8 times longer tliaa broad ; oosporangia mostly single, rarely 

 geminate, subovatc, in the lower portion broad, in the middle swollen, in the uiipcr part con- 

 tracted ; the 2 lateral pores situated above the middle ; oospore subglobose or broadly 

 ovate, its coats without markings; antheridia generally biccllular, sometimes tricellular, 

 numerous, placed generally upun the female filament cither upon or below the oosporangia. 



Remarks. — This species wiis found growing in a ratlicr stagnant brook in the 

 meadow by "Kobinson's Knoll," at the junction of the Schuylkill River and ^^■issa- 

 hickon Creek, near rhiladeli)hia. The filaments, which vary very greatly in size, 

 arc in their early history attached to dead leaves and sticks, but finally, I think, 

 float free in the water. The larger, fruit-bearing filaments arc remarkable for their 

 crookedness. None of the threads that I have seen ended in a seta-like portion. 



The fruit is produced in abtmdance, but very rarely is there more than a single 

 spore in any one place. The method of the formation of the sporangia dift'ers from 

 that of all the other CEdo<joiua which have come under my notice. Instead of 

 two cells being concerned but one cell is employed. The cell (fig. 2 a, pi. 1<S) that 

 is to be used for such a purpose grows much beyond the ordinary size, until it is 

 nearly or cpiite twice as large as its neighbors. All tlie time it is well filled with 

 chlorophyllous protoplasm. This now contracts and finally is all packed into the 

 upper half of the cell. At or even before this time the lateral openings become appa- 

 rent. There are two of them, situated just in the angle where the cell at its upper 

 end commences to contract to the size of its fellow. At this tim(> T think fertiliza- 

 tion takes place, although I have never actually seen the spermatozoids enter the 

 orifices. The cell (fig. 2h, pi. 17) now divides into two by forming a wall separa- 

 ting the lower empty half from the upper full one, which is to be the sporangium. 

 The contents of the latter now condense into a ball, and it itself becomes more tumid 

 in the middle. Finally a reddish-brown broadly globular spore (fig. 2 c, pi. 18) 

 is formed. I have not been able to make out more than one distinct thick coat. 

 The surface of the spore is smooth. The androsporcs are formed in a cell (fig. 

 2 (7, pi. 18) which has grown beyond the normal size and then divided into four 

 or five short cells, each of which gives origin, I believe, to a single androspore 

 in its interior. The antlieridia are numerous, from 2 to G being commonly attached 

 to the lower portion of the sporangium, or to the cells just beneath it. They 

 (fig. 2 (', pi. 18) have a rather large foot, and are generally curved at the base. The 

 distal of the two cells composing them is crowned with a little cap, and produces 

 (me or sometimes two spermatozoids. These (figs. 2 h and 2 (j, pi. 18) during their 

 escape arc always very much squeezed out of shape, but when free become globular 

 or slightly pear-shaped. They are highly transparent and contain a few green 

 granules. Their motion is at first slow, but soon becomes very active. The mode 

 of egress from the cell is obtained by the cutting off of the upper end of it, the 

 little cap opening like a trap-door. After this cell has been emptied, sometimes a 

 second similar one is foruKMl, wliich bears it aloft. 1 have never seen spermato- 

 zoids produced by this second cell. 



A. niintii, Wool). 



Filnm.T, plcrunupic in setam longam, terniinalem coloris e.tportam productum ; oogoniis pler- 

 iinKpie singulis, globosis, interdum nonnihil hexagoniis, medio nunnihil tiimidis, poro laterale 



