NUTRITIVE ORGANS OF CELLULAR PLANTS. 325 



to be replaced by that of divided filaments. There is 

 not, in fact, in these plants, any solution of continuity, 

 but they present kinds of transverse partitions, produced 

 by different causes; thus — 1st, if the filament be formed of 

 a simple series of cellules, perhaps enclosed in a mem- 

 branous sheath, the partitions which divide them are 

 visible to the eye on account of the transparency of 

 the tissue, forming what are falsely called articulations. 

 2d. It happens in some species that several cellules of 

 the same length are placed side by side, and the union 

 of their ends, seen collectively, produces the same ap- 

 pearances. 3d. I have also seen pretended articulated 

 filaments which were composed of cellules, alternately 

 very long and very short; the latter, when slightly 

 magnified, resembled partitions. It would be easy to 

 multiply these examples, but they are sufficient to 

 show that these filaments are not really articulated, 

 and that their appearances are owing to very different 

 causes. 



The genus Hydrodyction is very remarkable in its 

 anatomical structure ; it presents a purse-like sac, com- 

 posed of pentagonal meshes : at a certain age, the five 

 little filaments, which by their union form a mesh, 

 disunite, and each of them becomes a sac similar to 

 that of which it formed a part, and is composed in the 

 same manner, of pentagonal meshes. This example 

 tends to confirm the opinion of those who think that the 

 cellular tissue is developed by the swelling of the 

 granules contained in its interior. 



The Algae evidently appear to be the vegetable 

 family the structure of which approaches nearest to 

 that of animals. Several genera have forms so singular 

 that they can only be classed in one or the other king- 

 dom for physiological reasons, and not on account of 

 their organographical characters. Thus, the Oscillatorias 



