LICnENOLOGICAL MEMORABILIA. 123 



by others, and has been even wholly neglected and overlooked, and 

 that with contempt, by many Bavans. 



To determine what becomes of the zoospores after their issue 

 from the gonidia, M. Woronine has during two successive years 

 (1870-1871) carried on researches on the gonidia of Physcia pvl- 

 venrfenta, (Schrcb.), and in a paper in the Ann. des Sc. Nat., 

 ser. 5. Bot., vol. x\i., p. 317, illustrated by tab. 14, has published 

 the results. 



M. Woronine freed the gonidia from the thallus of this lichen, 

 and cultivated them on a stage of a microscope, and kept them 

 moistened daily with pure water. At the end of five days he saw 

 the nucleus and the great lateral vacuole found in every gonidium 

 to disappear, and the entire contents of the gonidium become very 

 finely granular, and transformed into a considerable number 

 (thirty, forty, or more) of small, round, irregular protoplastic 

 bodies, which are the future zoospores. During this time the 

 gonidia increased considerably in size, and on a certain part of 

 their surface a small protuberance arose, indicating the point 

 whence the zoospores would issue. When the zoospores were fully 

 formed, this protuberance increased very quickly ; the membrane of 

 the gonidium became in that point thinner and thinner, and ulti- 

 mately absorbed, and an aperture formed, from which issued the 

 entire mass of zoospores surrounded with a very delicate membrane. 

 This membrane quickly disappeared, and the freed zoospores dis- 

 persed themselves throughout the circumambient water. 



These zoospores are oblong and fusiform in shape, generally 

 more or less attenuated at one extremity, which is furnished with 

 two cilia, by means of which they move about with great rapidity. At 

 the end of five or six hours this movement ceased, and the zoospores 

 lost their cilia, took a perfectly round form, became covered with 

 a membrane, their contour more definite, and their size enlarged. 

 In about three more days these small spherical bodies assumed a 

 decided green tint, and in each of them a small but very distinct 

 central nucleus was observed. In fact, these small spherical bodies 

 assumed the form of small gonidia, precisely identical with those 

 contained in the large gonidia. In four or five days more these 

 young gonidia, obtained from the transformed zoospores, became 

 enlarged in size, and eventually began to multiply themselves by 

 the usual process of reiterated and successive division. During the 

 following five or six days these young gonidia grew considerably, 

 but ultimately perished, probably from deficiency of nutriment. 



These experiments he repeated several times, and always with 

 the same results, and he thence deduces that the zoospores pro- 

 duced from gonidia vegetating externally to the thallus, never 

 produce either filament or hypha, but continually give existence to 

 new colonies of young gonidia. 



Such are the results of M. Woronine's researches, which appear 

 to carry the previous researches of physiologists one step further, 

 viz., in witnessing the conversion of the zoospores into gonidia again. 



