244 



TiiALLUfnrT±::s. 



(2) The Peronosporeas^ live in the interior of Phanerogams, the branches of 

 their imicelhilar mycelium growing between the cells of the tissue from which they 

 draw their nourishment by peculiar organs of suction (Haustoria) (Fig. 168, A, h). The 

 mycelium produces first of all asexual fertile branches which project above the surface ; 

 in Peronospora they protrude through the stomata and branch in an arborescent 

 manner; in Gystopus they are club-shaped (Fig. 168, B) and closely packed, forming 

 a hymenium beneath the epidermis. The separated Conidia are in some species of 



Fig. 169. — Cystopus candidtis. A mycelium with young oogonia ; B oogonium og with oosphere os and antheridium an; 

 C ripe oogonium ; Z> ripe oospore ; E,F,G formation of swarm-spores from oospores ; z endospore (after De Barj') ( x 400). 



Peronospora simple spores, in others (as P. infestans), and in all species of Gystopus, 

 they are not immediately capable of germination, but when in contact with water, as for 

 instance drops of dew or rain, develope several zoospores (Fig. i68, C, Z), -E, i^). In 

 some species cf Gystopus the terminal member of each row of conidia is capable of 



is in fact one of true conjugation. Where there are no lateral branches fertilisation would seem to 

 be required by means of antherozoids. Max Cornu believes that the supposed spermatozoids discovered 

 by Pringsheim really belong to an endophyte of the group ChytridinecB, which have often been iden- 

 tified with organs of the plants they infest. He thinks it probable that the spermatozoids closely 

 resemble the zoospores in appearance, and have been overlooked in consequence. This is confirmed 

 by the process of fertilisation in Monoblepharis, the spermatozoids are half the size of the zoospores, 

 but of the same form. They creep with amoeboid movements over the wall of the oogonium and 

 fertilise the oosphere by blending with it, (See also Archer, Quart. Journ. Mic. Sc. 1867, p. 121. 

 —Ed.] 



^ De Bary, I.e. p. 176, and Ann. des Sci. Nat. 4th series, vol. XX. 



