FRESH-WATER ALG^ OF THE UNITED STATES. 83 



division, they are elliptical. They are of a bright green color and almost always 

 have a conspicuous rounded granule w^ithin them ; sometimes, but not commonly, at 

 one end there is a hyaline space or vesicle, similar to that seen in zoospores. I 

 have watched the production of zoospores in a plant gathered late in November. 

 The outer wall of the cell is always so thin as to be scarcely perceptible, and when 

 the zoospore is beginning to move, it looks as though the whole cell were rocking, 

 the thin outer coating being lost to sight. After a considerable period of vain 

 effort the zoospore escapes from the thick gelatinous mass which surrounds it. It 

 is biciliated, roundish, and furnished with a hyaline space at the end. 



I have observed a Tetraspora growing in rapidly running water, which some 

 would no doubt consider distinct, but which seems to me rather a variety. The 

 saccate frond was of a very vivid green, erect, buoyed up by an air-bubble con- 

 tained in its upper end. Its shape was that of a long sack widened very much 

 above, and below constricted into a fine point, by which it was firmly attached. 

 In some instances it attained a length of seven or eight inches. In aU other 

 respects these plants agreed with the others found in quiet water. 



The species of this genus are to me not at all well-defined in any work which I 

 have had access to. The plant now under consideration abounds everywhere in 

 this neighborhood, and is without doubt the one identified by Prof. Bailey as T. 

 gelatinosa (Vauch), of which, however, he afterwards states that Prof. Harvey, to 

 whom he had sent specimens, writes that it is a distinct species, and proposes to 

 call it perforata. In my Prodromus I referred the plant to T. luhrica (Roth). 

 My reasons for doing this were that the size of the cells corresponds very closely 

 with the measurements of that species as given by Prof. Kabenhorst, and the 

 absence of anything that seemed to me definite in the descriptions of the two 

 species. Moreover, if the possession of a parietal hyaline spot be not simply an 

 accident of growth, it would indicate that the plant belongs to P. luhrica. I do 

 not think, however, that any importance is to be attached to this, as the vacuole 

 is often absent, and, although Prof. Rabenhorst makes no mention of it, is, in all 

 probability, present in certain states or stages of T. gelatinosa. My own convic- 

 tion is, at present, that T. gelatinosa and T. luhrica are very probably synonyms. 

 If they be distinct, the plant from which the above description was taken is refer- 

 rible to T. perforata (Harvey), which, if not new, is a form of T. luhrica rather 

 than T. gelatinosa. If T. luhrica and T. gelatinosa be united, no grounds are left 

 for sustaining the separateness of T. perforata. 



Whilst botanizing in a primeval glade and forest, known as Bear Meadows, in 

 this State, I came across a spring, covered with a Tetraspora, which appears to 

 represent the T. gelatinosa type. It formed great masses half an inch in thickness, 

 at first attached, afterwards floating and covering the surface of the pool for several 

 feet each way. When young these masses were elongated and were formed of 

 numerous lobes attached often by very slender pedicles, and having their margins 

 thickened and undulated so as to give a beautiful waved appearance to the light 

 green mass. Under the microscope the structure was similar to that of the other 

 form, except that the cells varied more and attained a greater size. Their diame- 

 ters ranged from ^^J^/ = 0.00027" to ^^5^" = 000066". 



