KNOWLEDGE OF CRYPTOGAMOUS PLANTS. 253 



theVaucheria elavata DC, aiul i)roved that tLey possessed cilia as orgaus 

 of locomotiou, and that tliey genniiiated into a plant like tlie parent. 

 Many investigators have furnished further data concerning the 

 existence and the structure of these interesting bodies, but the 

 most complete researches were published by Thuret in h«is essay, ^^ Siir 

 Jes zoospores dcs aJgccs."' lie had observed zoospores in sereral hun- 

 dred species, and illustrated th.^ni in a masterly manner. We learn 

 from these investigations that the above spores are the unsexual organs 

 of reproduction in the algie, and may be compared to the buds of 

 higher plants. 



The interesting and instructive i)rocess of fructification in alga^, has 

 been studied with equal accuracy. Although the great physicist, 

 lleannnir, had suspected the existence of organs of fructilication in 

 fuci, Thuret was the lirst to prove it directly and scientifically. lie 

 demonstrated that the small indentations on the surface of the FucacccVy 

 the so-called conceptacles, contained both the male and female organs 

 of fructificntion, (the antheridia and oogonia;) he observed the forma- 

 tion of antherozoids and the penetration of the spermatic filaments into 

 them ; he explained how the spore was developed after fructification. 

 In fresh-water alga^, Pringsheim first succeeded in directly proving 

 the existence of fructifying organs in the Vauchcria, Ocdogonium, and 

 ColcocJia'te. Cohn followed with his interesting observations of the 

 ^Sphaeroplea annuUna and the Yolvocimv. These observations prove the 

 following mode of fructification in the alga^: the so-called seed fila- 

 ments penetrate the membraneless mass of the antherozoids, which are 

 then snrrounded by a cellular membrane and converted into stationary 

 spores. These are the direct opposites of zoosi^ores, and may be com- 

 I)ared to the seeds of higher plants. 



The results of this and many other researches have enabled us to 

 gain sufficient insight into the growth, reproduction, and propagation 

 of these plants, and it will be the task of coming investigators to con- 

 tinue the work on this basis. 



If we now turn to the classification of the algie, Ave shall see that 

 excursions to the different seas of every zone have enlarged our ac- 

 quaintance with the forms of this class. Excursions to the Antarctic 

 and to the northern part of the Pacific Ocean have furnished us with 

 the grandest specimens of lichens, and have shown us that marine 

 vegetation does not reach its highest development in the tropical 

 oceans, but m the Arctic and Antarctic polar seas. Kiitzing's and 

 Niigeli's contributions have already been mentioned. In the third sup- 

 plement to his Goieribus J*Jaiit(irum, Endlicher i)ublishe(l, together with 

 Diessing, a systematic table of this class, distinguished by the happy- 

 arrangement into families and genera. A very important work is 

 Species f/cnera ct ordincs aJgarnm, by Aghard the younger, which, al- 

 though it only contains the Fucoidcw and Floridea', surpasses all other 

 publications in the original natural grouping of his mattjrials, and by 



