226 THE VEGETABLE WORLD. 
tuberances now rise, which meet four similar ones in the opposite 
frustule, indicating the future channels by which the two frustules 
become united, as well as the spot where the double sporangium is 
afterwards developed. 
IL Conrervace#. 
Towards the close of the year, in autumn, on moist, humid days, 
or after a heavy fall of rain, we frequently meet on roadsides, or in 
garden alleys, small gelatinous, greenish masses, more or less 
globulous and folded up. These are a species of Nostoc, a kind 
of organism of which it is difficult to say whether it partakes most 
of the animal or vegetable world. 
In studying the organisation of 
these curious plants, we shall 
follow M. Thuret in the observa- 
tions he has made on Nostoc ver- 
rucose, which he found growing 
in the brooks in the neighbourhood 
of Paris, attached to submerged 
stones, upon which many indi- 
viduals had massed themselves together, forming on the stone 4 
carpet of blackish green (Fig. 296). Each Nostoc is a sort of 
irregular air-bag, as in Fig. 296, folded, rounded, 
and shut up, filled with greenish gelatinous matter, 
whose appearance and consistence forcibly reminds 
one of seed of the grape. In the bosom of a very 
abundant mass of this matter, we find numerous 
filaments, composed of spherical globules placed 
end to end like the beads of a chaplet, and inne 
of a bluish-green, granulous matter. Fig. 297 
represents the sort of chaplet which occuples the 
interior of the JV. verrucose, and accompantes 
the mucilaginous matter. When the plant 18 
surveyed in its full development, the inter 
pelicule formed by the thickened mucilage 18 YUP 
tured, and the green substance formed of mucilage 
Fig. 296. Mass of Nostoc, 
Fig. 297. ‘lity 
Chaplet of Neste. Hersed in the water with so much the more factity 
that it seems gifted at this stage of its existence with a very pereep- 
and of chaplets is left to escape. This matter isdis- 
