504 



CRYPTOGAMOUS OR FLOWERLESS PLANTS. 



of ambiguous nature, on account of the free movements they ex- 

 hibit (661) ; but these are nearly as well marked in Oscillaria, &c. 

 (Fig. 66). More ambiguous still, and on the lowest confines of 

 the vegetable kingdom, are those minute vegetables, as they 

 doubtless are, which constitute the 



1188 



1193 1199 1198 



1205 



949. Subord, Diatomaceae, These essentially differ from the last 

 in the brown instead of green color of their contents, in the sili- 

 ceous and durable nature of their cell-wall, and in being natives of 

 salt, instead of fresh water. Their movements, as they break up 

 from their connections, are still more vivid and varied. Some are 

 fixed (Fig. 1207) ; others are free. Some are extremely minute ; 

 others consist of clusters of cells of considerable size. 



FIG. 1188. Summit of the frond of Fucus vesiculosus. 1189. Section of one of the recepta- 

 cles. 1190. One of the contained globules. 1191. Spores and jointed filaments of which the 

 globules are composed. 1192. Delesseria Le Prieurii. 1193. The sterile plant. 1194. Magni- 

 fied portion of the fertile frond. 1195. Portion of the same, more magnified, showing its tissue 

 from the midrib to the margin. A. Theca, opened, with the spores. 1196. Portion of the 

 network of Hydrodyction utriculatum. 1197. A magnified joint, filled with the green matter 

 which developes into a new plant. 1198. Single filament of Tyndaridea cruciata, showing the 

 star-shaped bodies, enveloped in mucua. 1199. Two filaments of the same united side by side. 

 1200. Vaucheria geminata, in fruit. B. Vesicular receptacles, enlarged. The remaining fig- 

 ures represent some of the ambiguous Diatomaceae. 1201. Gonium glaucum, of Ehrenberg, 

 who thinks it a congeries of animalcules ; while Meyen has described it as an Alga. C. Closte- 

 rium Lunula ; usually filled with floating green globules : a, the perfect vegetable ; b, the same, 

 separating into two by spontaneous division ; c, an individual resulting from this spontaneous 

 division, developing a second ; d, two individuals conjugately united ; the green matter all 

 collected in the uniting globule. 1202. Euastrum Pecten, and 1203, E. Crux-Melitensis. 1204. 

 A Diatoma, breaking up into separate individuals. 1205. A Fragillaria. 1206. MeriJion circu- 

 lare, front and side views. 1207. Echinella flabellata; perhaps a group of animalcules. 



