254 Citicinnati Society of Natmal Ilistoiy. 



some writers. However, it is not well understood, and, indeed, it 

 seems probable that Ave are still far from a correct understanding 

 of the whole life of these strange plants. Many may be condi- 

 tions of higher plants, while the resemblance that the gonidia of 

 certain lichens bear to tlie nostoc filament has given rise to much 

 discussion as to the part our plant may play here. 



Although this agate-plant hardly agrees with any of the de- 

 scribed species, yet in the present state of our knowledge of the 

 genus, it is not advisable to consider it an entirely new species. 

 We will consider our plant a variety of Nostoc prnniforme. 



The size is quite variable; the largest observed were about an 

 inch and a half in diameter. The jelly is remarkably firm and is 

 inclosed in a leathery periderm. The shape may be called glo- 

 bose. In the central portion of the thai! us the filaments are curved 

 in the characteristic nostoc manner, but, running out from here, 

 they are arranged in almost straight lines radiating toward the 

 periphery, when they are again twisted and tangled, probably thus 

 helping to build up the periderm. The cells are more variable in 

 size than those of the iy\Aca.\ Nostoc pfiiiufonnc. No sheath can be 

 seen in a vegetating specimen. The manner of reproduction is 

 similar to what has been described for other species, with the ex- 

 ception that the whole process takes place within the parent thallus, 

 the Iior/iiogoiics not even breaking loose from adjoining cells. The 

 same filament frequently has different portions in all the different 

 stages of the reproductive process. 



The reproduction was observed in specimens collected in 

 August, the first step being the development of sheaths about por- 

 tions of the filaments. The cells inclosed then divide into rows 

 of cells after the manner described by Thuret. In reuniting these 

 cells do not seem to observe the regularity described for other spe- 

 cies, but the result is the same. 



Among the twisting filaments of the central portion of the 

 tliallus, the /loriiioi^oiics while forming are naturally very irregular 

 in shape. When fully formed they are nearly spherical, and the 

 inclosed cells are so closely pressed together that the regular fila- 

 ments, which could be traced before this stage, cannot be made 

 out. It seems probable that the parent must decay before these 

 young i)lants can develop into full grown nostocs. Whether or 

 not these are now in a condition to pass through a resting stage, I 

 cannot say. 



