GLOEOTRICHIA. 247 



Plate CLXXIX, fig. 10, two trichomes from a thallus 

 apparently in a state of dissolution, without maturing ; fig. 

 11, two trichomes with long spores, narrow sheath and 

 gonidia formed above the spores and passing out of the 

 sheath at the ruptured ends. 



GLOEOTRICHIA PISUM, Thur. 



Thallus rather soft, as a rule spherical, of the size of 

 mustard seeds to that of peas, attached to water plants, 

 various in color, brown, aeruginous or olive-green. Tri- 

 chomes elongated ; lower cells with a distinct sheath, cell 

 contents aeruginous, 1-2 times as long as broad ; upper cells 

 longer with sheaths indistinct. Sheaths always close simple, 

 not inflated or contracted. Spores cylindrical, rarely as 

 much as 30 times longer than the diameter. Heterocysts 

 usually wider than the vegetative cells. 



Diameter of spores, 5-12 yu ; of heterocysts, 7-14 //. 



Syn. Rivularia Pisum, Ag. ; It. durissina, Kg. ; It. Lens, Kg. ; 

 It. villosa, Eab. ; It. cartilaginea, Wood. 



Often very abundant, parasitic on water plants, but most 

 frequently seen without having the sheath developed. 



A very peculiar and perhaps novel mode of fruiting was 

 observed in specimens collected in a stagnant pool, Quaker- 

 town, Pa., August, 1879. The spores were long, about 

 twenty times longer than the diameter ; the contents of these 

 passed down, breaking through the wall separating between 

 the spore and the heterocyst, not only filling but greatly 

 expanding the heterocysts to a capacity to hold the larger 

 portion of the spore contents. Saw none quite empty, but 

 many more than half vacated. The subspherical, inflated 

 heterocysts were numerous, many separated from the spore 

 and scattered loosely ; assuming a vegetative green appear- 

 ance ; cell contents granular, forming possibly sporangia of 

 some kind. Facilities failed to trace these bodies to farther 

 development. 



The process of forming gonidia in the basal cells of plants 

 of this family has already been alluded to (vide page 236 and 

 Plate CLXXI). This appears to be another way, perhaps 

 abnormal way of propagation. 



Plate CLXXIX, fig. 7, part of a thallus, filaments show 

 the spore cases partly emptied ; the contents emptying into 

 the enlarged heterocysts ; figs. 8, 9, small sections from other 

 thalli which did not show the same process, because not in 

 proper condition for it ; fig. 9, shows gonidia or cells, and 

 ormogonia passing upward ; fig. 6, natural size of thalli ; 



