334 KEPRODCCTION IN 



658. Direct Fertilization of Spores by Spcrmatozoids from an Antlie- 



ridium J the latter answering to the anther, or essential part of the 

 stamen, of PhoBnogamous plants. Cohn * has shown that even 

 Volvox — an undoubted vegetable, consisting of microscopic one- 

 celled plants of rounded form, grouped into a spherical colony — has 

 a true sexual propagation, like that of the higher green Alga?, some 

 of the individuals or cells of the sphere producing anlheridia or fer- 

 tilizing cells, while others produce spores, or bodies which become 

 such on being fertilized by the antheridia, which alone renders them 

 capable of germination. A good general idea of bisexual reproduction 

 in the simplest Algaj may best be obtained from a brief abstract of 

 what has lately been discovered by Pringslieim and Cohn in two or 

 three common species of comparatively easy investigation. 



G59. Vaucheria is a genus of several species of green Alga;, con- 

 sisting of simple but indefinitely branching cells (Fig. 89). In fruc- 

 tification, the whole contents of the more or less enlarged extremity 

 of some of the branches, or of a special projection from the side 

 of the cell, separate from the general contents of the plant, con- 

 dense into a globular green mass (Fig. 89 a), and become a spore, 

 which at length escapes by a rupture of the walls (Fig. 90), moves 

 freely about in the water for some hours, then fixes itself, and ger- 

 minates, elongating directly into a thread-like and at length branch- 

 ing plant, like the parent. Here there appears, and was generally 

 thought to be, reproduction without fecundation. Vaucher, however, 

 more than half a century ago, noticed one or more horn-shaped pro- 

 jections in the vicinity of the spore-bearing portion, which he sus- 

 pected to be the analogues of the anther. Nothing had been found 

 to verify this view until the year 1854, when Pringslieim, of Berlin, 

 discovered the fecundation and verified this conjecture. The horn- 

 shaped body is an antheridium, or the analogue of the anther. It 

 produces myriads of extremely minute corpuscles, of oblong shape, 

 and furnished with a bristle or cilia at each end, by the vibration of 

 which they move freely in the water. These are spermatozoids (so 

 called from their obvious resemblance to the spermatozoa of ani- 

 malo), and the analogues of pollen. At the proper time the anthe- 

 ridium bursts at the summit, and discharges the spermatozoids ; at 

 this time the wall of the projection which contains the spore likewise 

 opens ; numbers of the free-moving spermatozoids find their way 



* In Comptes Rendus, vol. 43, 1856, and Ann. Sci. Nat. ser. i, vol. 5, p. 323. 



