258 



BOTANY. 



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

 numbers of salmon and otlier kinds of fisli were destroyed by one of the 

 common species, Saprolegnia ferax.* 



342— Order Peronosporese. 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- 



U^ 



Pre. ITO. 



Fig. 174.— A Tegetative hypha, m, m, of Peronospara calotheca from the tissue of 

 Asperula satwa. The two celle hetween z z are filled with the long branching haus- 

 toria from the hjjpha m, m. X 380.— After De Bary. 



Fig. 175.— Conidia-bearing hyphge of Peronosporn infestans. a, formation of the 

 firpt conidia upon the ends of slender pedicels ; 6, the formation of the second and 

 third conidia ; the pedicel is prolil'erouB 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. 



liarly formed lateral branches (haustoria), which thrust 

 themselves through their walls (Fig. 174, and Pig. 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 " Jalirbuclier fiir WissenscliaftlicheBotanik," Vol. IX., p. 389, 

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

 XV. 



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

 p. 1.53. 



