144- BRAUN, ON UNICELLULAR ALG/E. 



germinate^ some require fecundation^ others germinate spon- 

 taneovisly^ some at once_, others after a long or shorter term 

 of restj some in totality, others after throwing oft" the peri- 

 spore ; most producing only a single individual, whilst some 

 (under a divided germination) give rise to several individuals.^ 

 Propagative corpuscles (spores), moreover, also occur, either 

 bicellular or multicellular. This being the case, a diversity 

 of terms also becomes requisite, but what these should be, 

 and upon what principle they should be framed, is at present 

 not easy to determine, seeing that numerous considerations 

 relative both to the origin and to the structure of the propa- 

 gative cells, but more especially concerning their physio- 

 logical import, fecundation, and germination, have not as yet 

 been sufficiently inquired into. The terms, therefore, here 

 set forth are proposed more for the temporary purpose of 

 their being considered and judged of, than for use. 



The author, in his work on ' Rejuvenescence in Plants,' 

 p. 143, has endeavoured acciu'ately to determine the diffe- 

 rence between spores and goriidia, a difference which, at the 

 present day, though difficult to sustain, it is neither incon- 

 gruous nor useless to discuss. Gonidia are formed either in 

 the vegetative cells themselves, or in cells only slightly 

 differing from the vegetative character, filled with the same 

 material, and for the most part resembling the vegetative 

 cells in natm-e and colour ; so that they represent, as it were, 

 a cytoplasma liberated from the envelopes. Covered with a 

 special delicate and soft integument, they proceed to germi- 

 nate at once and in totality. From gonidia, which move by 

 means of vibratile cilia, a transition to ciliated spermatozoids 

 is afforded through the sterile microgonidia.f Spores, on the 

 other hand, originate within cells more widely differing from 

 the common vegetative cell, and are themselves distinguished 

 by the altered nature of the contents and their peculiar 

 colour. Furnished with special coats, dovible or multiple, 



* The multicellular spores of most Lichens and Ascomycetes, many 

 Gymiioinycetes, and also of some Hymeuomycetes (Tulasue, 'Aun. d. Sc. 

 Nat.,' Ill, 9, p. 215, 1. 13, Iktcrymyces), represent in all respects compound 

 spores, protruding in like manner from every cell, germinal lilaments. The 

 raulticcUular spores of Pellia (' Hofmcister vergl. Untcrs.,' p. 10, t. 4 ; 

 Groaland, in ' Aun. des Sc. Nat.,' IV, p. 13, t. 2), are of a different nature, 

 representing a single germinal plantule, formed by a premature division of 

 the primordial cell. 



-j- Whether the gonidia of Lichens are altogether analogous with tliosc 

 of Algce is not quite clear. Endogenous, as it would seem, in their origin, 

 they agree with tlie gonidia of Alij/r, but remaining within the texture of 

 the i/iullus they are changed into free vegetative cells, wliicii produce new 

 and repeated series of gonidia. 



