26i ALDROVANDA VESICULOSA. [Chap. XIV. 



Germany. Ab I can add nothing to Prof. Cohn's excellent 

 description, I will give only two illustrations, one of a 

 whorl of leaves copied from his work, and the other of a leaf 

 pressed flat open, drawn by my son Francis. I will, however, 

 append a few remarks on the differences between this plant 

 and Dionffia. 



Aldrovanda is destitute of roots and floats freely in the 

 water. The leaves are arranged in whorls round the stem. 

 Their broad petioles terminate in from four to six rigid pro- 

 jections,* each tipped with a stiff, short bristle. The bilobed 

 leaf, with the midrib likewise tipped with a bristle, stands 

 in the midst of these projections, and is evidently defended 

 by them. The lobes are formed of very delicate tissue, so as 

 to be translucent; they open, according to Cohn, about as 

 much as the two valves of a living mussel-shell, therefore 

 even less than the lobes of Dionrea; and this must make the 

 capture of aquatic animals more easy. The outside of the 

 leaves and the petioles are covered with minute two-armed 

 papillae, evidently answering to the eight-rayed papillae of 

 Diona>a. 



Each lobe rather exceeds a semi-circle in convexity, and 

 consists of two very different concentric portions; the inner 

 and lesser portion, or that next to the midrib, is slightly 

 concave, and is formed, according to Cohn, of three layers of 

 cells. Its upper surface is studded with colourless glands 

 like, but more simple than, those of Dioncea; they are sup- 

 ported on distinct footstalks, consisting of two rows of cells. 

 The outer and broader portion of the lobe is flat and very 

 thin, being formed of only two layers of cells.* Its upper 

 surface does not bear any glands, but, in their place, small 

 quadrifid processes, each consisting of four tapering pro- 

 jections, which rise from a common prominence. These pro- 

 cesses arc formed of very delicate membrane lined with a 

 layer of protoplasm ; and they sometimes contain aggregated 



There ban been much discus- 1850) and Caspary ( Bot. Zel- 

 lon by botanlHtM on the homo- tiing,' 1850). the two layers of 

 logical nature of these nrojee- cells ore so comtiiiied ns to pro- 

 tlons. Dr. Nltscbke (' Bot Zel- diiee the effect of a HliiRle layer, 

 tang,' 1801, p. 140) believes that The three layers of which the 

 they correspond with the flmbri- centnil part Is made up consist 

 ated scale-like bodies found at of external and Internal eplder- 

 the bases of the petioles of Dro- nilc layers, and a single layer of 

 erm. parenchyma. P. D.] 



* According to Cohn (* Flora,' 



