88 INTRODUCTION TO CRYPTOGAMIC BOTANY. 



can scarcely be otherwise than more or less heterogeneous, 

 could not fail to be instructive ; and might lead to results which, 

 if they did not confirm the views so commonly entertained ia 

 Germany, would have an influence on science which it is diffi- 

 cult at present to appreciate." 



67. For a long time, motion, as said above, especially if it had 

 the semblance of being voluntary, was esteemed a certain mark 

 of discrimination between the animal and vegetable kingdoms. 

 Mere molecular motion, or that due to evaporation on the field 

 of the microscope, was therefore often brought forward as an 

 argument for the exclusion of many vegetables from their 

 proper position in the organised world. And there is the same 

 disposition occasionally now.* To take the example alluded 

 to before of Ulothrix (p. 18), and there are many similar ex- 

 amples, as Conferva glcnnerata, Achlya iwolifera, &c., the 

 articidations give rise, from their protoplasm, to cells termi- 

 nated by delicate cilia, by means of which, they move about 

 apparently at will, till the appendages lose their activity, and 

 the body sinks, becomes fixed at one end, and at the other 

 produces a new individual precisely like that from which it 

 originally sprang. Sometimes, as in Stilophora rhizodes,-f 

 there are two distinct formations of such bodies, from distinct 

 parts of the plant, both of them equally endowed with motion, 

 and both equally capable of reproducing a plant like the 

 original, though not precisely by the same series of phenomena. 

 These bodies are, moreover, so like certain Infusoria, as Disel- 

 TYiis, Dujard., that without ascertaining the changes which 

 take place during the course of their existence, it would be 



* See a notice of the motions of Navicula Vichiensis, Petit, by M. 

 Petit, in Montague's Sylloge Gen. et Spec. Crypt., p. 471. 



t Thnret, Eecberches sur les Zoospores des Algues, Partie 1, tab. 28. 

 In other cases, doubtless, two kinds of Zoospores are produced, as in 

 Leathesia and Mesoglcea, as they have the two organs called Oosporangia 

 and Trichosporangia by Thuret. The Zoospores of the latter are rather 

 larger than the former. In Cutleria, there are bodies answering to 

 autheridia, producing apparently Spermatozoids, but though they do 

 not germinate, they do not seem to have the power of impregnation. 

 They appear, in fact, to be a distinct transition from Spermatozoids to 

 Zoospores.— ^A^ireit, 1. c. tab. 26, 27, 31 ; Partie 2, tab. 1. 



