12 INTRODUCTION. 



So extraordinary were the statements from time to time 

 put forth rehitive to the sj^ontaneous motion of the reproduc- 

 tive germs of many Algce — a class of productions always re- 

 garded as vegetable — considered to be, that many observers, 

 and some do even now, refuse to give their belief to then- 

 accuracy. So numerous are the observers who have witnessed 

 the sino-ular motions above recorded, that the facts announced 

 in reference to them must be regarded as amongst those 

 which ought to be generally received and adopted. For a 

 long time I myself doubted the reality of the existence of 

 zoospores ; I have now satisfied myself on this head, having 

 repeatedly witnessed their movements in very many Conferv<B^ 

 but never as yet in any species belonging to the conjugative 

 tribe of Algce. ; in which, however, Agardli declares himself 

 to have witnessed it. For extended observations on the 

 motion of the zoospores of the Algm, see, in " Annales des 

 Sciences Naturelles (Botanique), 1836," a memoir " Sur la 

 Propagation des Algues. Par J. G. Agardh. Extrait." 



It is surprising that, out of the number of those 

 who now study the AlgcB, so few should have witnessed 

 the singular motion of the zoospores. The spring is the 

 best season for observing these bodies. If, at that time, 

 a number of Algce, collected indiscriminately from different 

 localities, are placed in a vessel of water over-night, and 

 allowed to remain undisturbed until the morning, usually 

 there will be noticed on the surface of the water a thin 

 green pellicle or scum : this, when examined, wiU be found 

 to consist of the zoospores of different species of Confervcs, 

 in all possible stages of developement. Their motion is 

 most active early in the morning ; and they would appear 

 to shun the light, as they are generally met with on the 

 side of the vessel farthest removed therefrom. 



Next in interest to the discovery of the zoospores them- 

 selves, and for which science was mainly indebted to the 

 researches of J. G. Agardh, is that of the means by which 

 their motion is effected. J. G. Ao^ardh declared that it 

 depended upon the movement of a prolongation or beak, 

 with which each zoospore was said to be furnished ; others 



