IN THE VEGETABLE KINGDOM. 37 



frond. According to the observations of Thuret on dif- 

 ferent species of Fucus, impregnation is effected by the 

 simultaneous evacuation of both elements from their re- 

 spective envelopes. During the recess of the tide, when 

 the tissues contract somewhat by desiccation in the air, the 

 antheridial cells are expelled, as well as the contents of the 

 so-called spores, consisting of eight protoplasmic bodies 

 enveloped in a gelatinous mucus. On being again sub- 

 merged, the antheridia rupture by imbibition, and the 

 antherozoids come in contact with the germinal bodies. 

 In about twenty-four hours after this, the gelatinous layer, 

 which surrounds each germ mass, is converted into a tough 

 membrane, in which Pringsheim mentions observing certain 

 red corpuscules, which he considers to be the nuclei of the 

 antherozoids.* Then follows germination a simple process 

 of cell-formation, resulting in the production of a new 

 frond. In some fucoids, however, the cells first formed in 

 this process separate from one another, being set free by the 

 rupture of the common investing membrane of the spore ; 

 and each of them may give origin to a distinct plant or 

 phytoid. 



Zoospores are now known to occur in this group also, but 

 no obvious alternation of forms has ever been observed. 



It would seem, therefore, that the only general conclu- 

 sion in regard to the reproduction of the Algse which, in our 

 present defective state of information, we are warranted in 

 drawing is this : that a sexual act probably occurs normally 

 from time to time in the life-history of all the species, 

 though impregnation has been actually observed only in a 

 few. We know, indeed, that non-sexual propagation prevails 

 to a great extent and in great variety of forms. Not only 

 is there the usual pullulation of new shoots, characteristic 

 of vegetables generally, which is here represented by the 



* Journ. of Micros. Science, IV., 125 (An. des Sciences Nat.) 



