102 Clark — jffolophytie Plankton of Lakes Atitlan and AmatMan. 



quite common in some of the samples of plankton. Wolle (F. W. Alg. 

 U. S. 189) regards Hormospora as a "pseudo-genus " composed of stages 

 of degeneration'of filaments of Ulothrix, Conferva, etc. All the specimens 

 seen were much alike, showing no young stages nor mature forms. More- 

 over, there was no other alga present that could readily give rise to such 

 forms. This alga was found in samples 4, 5 and (>. 



25. Microspore fontinalis (Berkeley). 



Conferva fontinalis Berkeley, in Sowerby, Eng. Bot. 2i>, pi. 2054, 1809; 

 Wolle, F. W. Alg. IT. S. 141, pi. CCX, figs. 17-20, 1887. 



I identify with the species called Conferva fontinalis Berk., by Wolle, 

 an alga which occurs somewhat sparsely through the plankton, most 

 abundantly in sample 5, from near St. Lucas, February 16. No form of 

 reproduction was observed, and the chlorophyl is aggregated in the center 

 of the cell, appearing in the form of small elliptical globoids, somewhat 

 suggesting gonidia ready to escape; cell-walls thin; diameter of filament 

 l<S/u; length of cells about 190/*. 



Precisely the same as the above in structure and appearance, but differ- 

 ing markedly in size (diameter 3.5/*, length of cells 38/*) are forms which 

 would for the present better be regarded as young individuals of the same 

 species. They occur abundantly among the filamentous material of the 

 greater number of samples from Lake Amatitlan. 



Wolle gives the characters of " Conferva fontinalis " as " diameter of 

 filaments 15-18/*, articulations 6-10 times as long as wide " and reports it 

 from fresh-water ponds and lakes in Florida. In looking up the original 

 description of Conferva fontinalis, I find it to be very poorly defined. 

 Wolle' s plant does not appear to be the same species, but it is a form with 

 such a complete absence of diagnostic characteristics that I prefer to let it 

 stand as it is. 



26. Conferva gyrans Clark sp. now 



Diagnosis: Filaments simple, rather short, consisting of about 3-8 cylin- 

 drical cells, the whole plant-form assuming the shape of an open spiral; 

 cells three times as long as wide. Plants exceedingly various in size, 

 the largest being 25/* in diameter with cells 80/* long. Cell walls thin, 

 chloropasts in formalin materia] bright green, elongate or spherical, ar- 

 ranged irregularly in the center of the cell; ends of filaments truncate, 

 formed by one of the former septa?, the remains of the old cell-walls 

 projecting beyond, and suggesting that the terminal cells may allow their 

 contents to escape as reproductive bodies, and then gradually break down. 

 Type material, plankton sample No. 3. Collected in Lake Atitlan, < iuate- 

 mala, in front of the hotel, February is, 1906, 9 p. m., by Dr. S. E. Meek. 

 The type material will he deposited in the U. S. National Museum. 



Scattered through the plankton samples from bake Atitlan, nowhere 

 abundant, but occurring quite commonly in some samples, is.an alga which 

 is unlike anything of which I can find any description or figures. The 

 filaments are twisted in the form of a corkscrew , and are very inconspicu- 

 ous, hardly visible to the naked eye because of their transparency. They 



