258 



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, Saprolegnia ferax.* 



342. Order Peronosporeae. 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. 174. 



FIG. 175. 



Fig. 174. A vegetative hypha, m, m, of Peronosnora calotheca from the tisene of 

 Asjterula sativa. The two cells between z a are filled with the long branching haus- 

 toria from the hypha m, m. X 390. After De Bary. 



Fig. 175. Coniaia-bearing hyphse of Peronoapora infestans. a, formation of the 

 first conidia upon the ends of slender pedicels ; b, the formation of the second and 

 third conidia ; 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 300. After De Bary. 



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 " Grevillea," Vol. I., p. 117. See also Prings- 

 heim's " Jahrbucher fur Wissenschaftliche 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. 



