VAUCHERIA. 



[ 808 ] 



VAUCHERIA. 



iodine) : no cellulose membrane exists at 

 this time ; and the <i:oiiidiiuu swims .about 

 actively inth e water, rovolvinf^ on its long 

 axis. The large number of cilia existing on 



Fig. 795. 



Fig. 796. 



Vauoheria Ungeri. 



Pig. 795. End of the filament from wliich the gonidiimi 

 has escaped. Majjiiilied 50 diameters. 



Pig. 79i5. Gonidiuin which has been treated with 

 iodine and dried between two slips of glass, showing 

 the cilia very clearly. Magniiied 110 diameters. 



this gonidium . distinguish it remarkably 

 from all others ; but we are inclined to be- 

 lieve that there is a nearer relationship than 

 appears at first sight. The green substance 

 at the surface of the gonidium presents a 

 pecidiar granular or globidar appearance; 

 and it appears not far-fetched to regard this 

 body as composed of a densely combined 

 family of ordinary two- or four-ciliated 

 zoospores, such as would be formed by the 

 swarming-spores of Hydrodictyon if they 

 remained in theii' primitive crowded con- 

 dition. This, however, is a point requiring 

 further examination. The end of the tube 

 from which the gonidium has escaped ap- 

 pears as a hyaline sac (fig. 795 j, which soon 

 decays down to the point where the con- 

 tents parted, where a septum, now closing 

 the tube, is developed. 



After swimming about for some time, 

 from one to several hours (usually about 

 two), the gonidium falls to the bottom of 

 the vessel, its cilia disappear, and it assumes 

 a spherical form, acquiring very soon a di- 

 stinct cellulose coat ; after this it soon ger- 

 minates by pushing out one or more tubular 

 processes (fig. 797), which grow up into 

 filaments like the parent. Sometimes the 

 gonidium cannot make its escape ; sometimes 

 half of it escapes and becomes pinched oft, 

 the other half being left behind : in these 

 cases, the arrested body, or the remaining 

 portion of the divided one, germinates in 

 situ (fig. 798). 



It should be mentioned that the contents 



of the vegetative filaments have a remark- 

 able tenacity of life ; for if the tube is slightly 



Fig. 797. 



Fig. 798. 



Vaucheria Ungeri. 



Fig. 797. G-onidia germinating, 

 diameters. 



Fig. 79S. Filament with gonidia germinating in the 

 parent tube; the left-hand figure, hal'' '- ' ' 

 diuia. Magniiied 25 diameters. 



Magnified about 15 



germinating in the 

 naif a divided goni- 



injured at any point, the primordial utricle 

 commonly retracts from the wound, and 

 secretes a cellulose layer (Xi its surface, 

 shutting off" the injured part. Filaments 

 are sometimes met with having several 

 living regions of this kind, shooting out 

 into branches, separated from each other 

 by dead, empty lengths of the filament. 



Besides the vegetative reproduction above 

 described, the Vaucherice are repz'oduced by 

 spores formed by the concurrence of two 

 distinct kinds of reproductive organs. Fila- 

 ments growing on damp ground ordinarily 

 exhibit lateral organs of two kinds, asso- 

 ciated together, but variously gi-ouped and 

 collected in varying numbers at particular 

 points, apparently according to external 

 conditions. The larger kind of organ, or 

 sporangium, appears first as a pouch-like 

 process, which expands into a short flask- 

 shaped body, stalked or sessile, the neck of 

 which is gradually turned over in the 

 development, until it projects at one side ; 

 the form then somewhat resembling that of 

 a bird's head (or a chemist's glass retort cut 

 off short at the neck, PL o. fig. 12 a, b, s). 

 Near this, on the main filament, or on a 

 common pedicel with one or more of the spo- 

 rangia, is developed another organ, the an- 

 theridiuni, at first straight and tubular, but 

 soon curving over into the form of a hook or 

 scroll, without however expanding (PI. 5. 

 fig. 12 A, B, a). The sporangium becomes 

 filled with dense green granular matter, and 

 cut off" by a septum from the main filament, 



3f2 



