35 PLANT DISEASES 



Sporangia scattered, or several in a cell, globose, with 

 a thin, colourless wall and a long, slender tube, which 

 often passes through four or five layers of cells to reach 

 the surface of the host. Swarmspores globose, oneciliate, 

 with a glistening oildrop, and a vacuole. Resting-spores 

 colourless or yellowish, solitary or clustered, thick-walled, 

 warted. Germination unknown. 



Saprolegniaceae. Asexual reproduction by zoospores 

 formed in zoosporangia borne on the hyphae ; sexual 

 reproduction by antheridia and oospheres, producing 

 oospores. 



Pythium, Pringsh. Mycelium parasitic in living plants, 

 intra- and intercellular; zoosporangia usually terminal, 

 wall thin ; zoospores always naked; resting conidia inter- 

 stitial or terminal, often produced in large numbers ; 

 oogonia monosporous ; wall of oospore colourless, smooth 

 or ornamented. 



Pythium de baryanum, Hesse, Ueber Pythium, etc., 

 Hallenser Dissertat, 1874. Mycelium branched, septa 

 rare ; resting conidia spherical, thin-walled, terminating 

 short branches, or interstitial, 20-25 \ L diam. Zoospo- 

 rangia globose or broadly elliptical, often shortly papillate, 

 terminal or intercalary; oogonia globose, membrane not 

 perforated; oospores globose, wall colourless, smooth, 15- 

 18 /A diam., forming a mycelium, and not zoospores, on 

 germination. Antheridia clavate, on very short branches 

 immediately below the oogonia, or on distinct branches. 



Pythium intermedium, De Bary, Bot. Ztg., 1881, p. 554, 

 tab. v., f. 14-16. Conidia terminal, globose, in chains of 

 2-5, terminal one largest, 18-24 n diam., on germination 



