306 BOTANICAL GAZETTE. 



ber of dried specimens of our species. I have incorporated in 

 the list the species mentioned by Harkness and Moore in their 

 catalogue of the Pacific Coast Fungi, 1 although, with a few ex- 

 ceptions, I have not examined specimens myself, but have given 

 them on the authority of Dr. Harkness. 



Our exact knowledge of the development and systematic 

 position of the Peronosporeae dates from DeBary 's classic mono- 

 graph, Recherehes sitr le developpement de quelques champignons 

 parasites, 2 published in 1863, in which were described the greater 

 part of our species. In a subsequent memoir, Untersuehungen 

 Ueber die Peronosporeen und Saprolegnieen;' published in 1881, 

 DeBary gives his views on the nature of the reproduction in 

 Peronosporeoe, and their relation to allied orders of fungi, so that, 

 except perhaps with regard to the germination of the oospores, 

 there remains almost nothing to be studied in connection with 

 the history of the development of this group of fungi. 



In his last paper DeBary includes in the Peronosporecv four 

 genera : Pythium, Phytophthora, Peronospora, and Cystopus. In 

 this country the species of Pythium have not been sufficiently 

 studied, and no mention is made of them in this paper, although 

 they possess a decided agricultural interest, since one species ap- 

 parently causes what is known in some parts of the Eastern 

 States as the potting bed fungus, which is very destructive to 

 young house plants in the winter. Other species are known in 

 decaying plants in damp ground. The species of the three re- 

 maining genera attack living plants, especially herbaceous exo- 

 gens, and produce their oospores or resting spores in the interior 

 of the leaves and young stems and bear their conidial spores on 

 the surface. The oospores of all three genera are similar and 

 produced in the same way, which can be learned from any of the 

 recent text books of botany. They are globose and borne singly 

 in an oogonium. They have two coats, the inner (Endospore) 

 of which is first formed, while the outer (Exospore or Epispore) 

 is formed, if one can say so, by a condensation of the surround- 

 ing protoplasm upon the endospore. In this way there is formed 

 on the outer part of the oospore a covering which is either nearly 

 smooth or marked with folds, ridges, or reticulations. 



The three genera can not be distinguished from one another 

 by their oospores, but the conidial spores serve to mark the 



KJal. Acad. Science, Feb. 2, 1880. 

 2 Annales des Sciences Naturelles, 4 Serie. T. 20. 



8 Beitr;ige zur Morphologie und Physiologie der Pilze. DeBary & Wor- 

 onin. 4 Reihe. 



