The Scottish Naturalist. 83 



Pythium Pringsheim. Mycelium delicate, growing in tissues 

 of dead plants or animals, or less often, in living bodies, 

 which it destroys. Organs of reproduction develop fully 

 in water ; they consist of zoosporangia at the tips of 

 branches. Zoospores form in the protoplasm, after 

 escape from the sporangium into the water. Oospores 

 formed singly in oogonia in cells of mycelium, or in 

 lateral branches. 



P. De Baryanum Hesse (=P. Equiseti Sadebeck). Parasitic 

 in living plants in damp places, destroying the plants 

 and forming numerous zoospores in the surrounding 

 moisture. Zoosporangia globular, or broadly elliptical, 

 usually on thin-walled Branches, emptied of their cell 

 contents. Protoplasm of zoosporangium escapes through 

 a long beak before the formation of zoospores. Oospores 

 round, 10-n (25-35, Schroeter) diam, rather thick-walled, 

 yellowish. 

 In Scotland, this species has been observed only in Equisetum 

 limosum near Aberdeen ; but it has been recorded from 

 England by Mr. W. G. Smith (sub nom. Equiseti) from 

 Potato plants ; and in Germany it is fatal to seedlings of 

 many plants, e.g., cresses and clover. Pythium (sp ?) 

 has been observed near Aberdeen in d^ad stems of 

 Epilobium and of Plantago. 



PeroilOSpora densa Rabh. Mycelium bears unbranchec 

 haustoria ; Conidiophores crowded into compact clusters, 

 at first a pure white, but becoming dirty yellowish-white, 

 erect, 150-200 high, towards the apex bearing from 2 to 

 4 straight branches, the lower of which may bifurcate, 

 but usually all bear only from 1 to 4 straight blunt 

 branchlets. Conidia vary from ovate to nearly globular, 

 usually about 15-16 by 12-13 > apex bears a low papilla. 

 Oospores (said to be globular, with a thin, yellowish 

 cell-wall) not yet observed in Scotland. Specimens from 

 Cults, near Aberdeen, have the lower branches bifur- 

 cated twice or thrice. 



P. Myosotidis De Bary. Conidiophores crowded in white or 

 gray clusters, erect, six to nine times bifurcated, ending 

 in slender, slightly-recurved branchlets. Conidia spheri- 

 cal (14-16 diam) or ovate, 20 by 15-16, hyaline, contents 



