253 



BOTANY. 



ing the year 1878, and for a year or two previous to that date, large 

 numbers of salmon and other kinds of fish were destroyed by one of the 

 common species, Saprolegniaferax.* 



342. Order Peronosporeee. The plants of this order 

 live parasitically in the interior of higher plants. They are 

 composed of long branching tubes, whose cavities are con- 

 tinuous throughout. They grow between the cells of their 

 hosts, and draw nourishment from them by means of pecu- 



FIG. 175. 



Fig. 174. A vegetative hypha, m, m, of Peronotpora calotheca from the tissue of 

 Asj)eriiln tativa. The two cells between t e are filled with the long branching haus- 

 toria from the hvpha m. m. X 390. After De Bary. 



Fijr. 175.-Conidia-b ' 

 first conidia upon the 



third < onidia ; the pedicel is proliferous from the base of each conidium after it is 

 formed, and thus the conidia, which are actually terminal, come to appear lateral. 

 X 200.-After De Bary. 



lia-bearing hyphW of Peronosponi infeatans. a, formation of the 

 i the ends of slender pedicels ; b, the formation of the second and 



liarly formed lateral branches (haustoria), which thrust 

 themselves through their walls (Fig. 174, and Fig. 176, A, h). 

 The vegetative growth is entirely within the host, and also 



and a translation in " Grevillen," Vol. I., p. 117. See also Prings- 

 heim's " Jahrbucher fur Wissenschaftliclie Botanik," Vol. IX., p. 289, 

 and Max Cornu, in " Annales des Sciences Naturelles," 5e ser., torn. 

 XV. 



* See a description by W. G. Smith in " Grevillea," Vol. VI., 1878, 

 p. 152. 



