BOTANICAL GAZETTE. 333 



I am not at present able to state certainly whether the American plant is P. 

 Parietarice, although it probably is not. Our species is probably of limited 

 range, and we must look to Erof. Burrill to discover the oospores and the mode 

 of germination of the conidia. Here again the resemblance to the other pin- 

 nate species would lead us to suspect germination by means of zoospores. 



b. Conidiophores dichotomous. 



29. P. sordida Berk. 



Ann. & Mag. Nat. Hist. 1861, 449; Cat. Pac. Fung. 29. 



"Forming broad, irregular, dirty, pallid spots on the under 

 side of the leaves ; threads loosely dichotomous above ; tips forked, 

 unequal ; spores obovate, apiculate, .001 inch long." Berkley 1. c. 



On Serophularia Californica. 



California (Harkness). Europe. 



30. P. spars A Berk. 



Gardener's Chronicle 1862 p. 308; Cat. Pac. Fung. 29. 



Conidiophores scattered, repeatedly dichotomous. Conidia 

 ellipsoid, apex obtuse. 

 On Rosa Californica. 

 California (Harkness). Europe. 



31. P. LOPHANTHI. 



Conidiophores very slender, long, naked below, above re- 

 peatedly dichotomous, divisions flexuous. Tips flexuous, forci- 

 pate, one division usually considerably longer than the other. 

 Conidia small, globose, or ovate-obtuse, 19-22/* by 15-20//, violet 

 colored. Oospores ? 



On Lophanthu8 scrophularicefoliv.s. 



Charles City, Iowa. (Arthur.) 



This species, which has only been collected by Prof. Arthur, forms small, 

 dirty-white patches on the under side of the leaves. It differs from P. Lamii 

 A. Br. in being much more slender and in not having pedicellate conidia. Its 

 relation to P. Calaminlhce Fuckel requires further study, and one needs to see 

 the oospores before concluding that the species is a good one. The conidio- 

 phores arc more slender and longer than in most of our species, in this respect 

 resembling the form on Oeum. The tips are bifurcate, one division usually 

 being much shorter than the other. 



The above includes all our species of Peronosporce, about which I have as 

 yet direct information. There are, however, several more species known to others, 

 I believe. The list of our species is by no means meagre, and it will probably 

 soon be increased, now that a number of observers are in the field. I have al- 

 ready, in a previous paper, called attention to the fact that our flora is charac- 

 terized by the abundance of species whose conidia germinate by zoospores, and 

 if, as is not unlikely, it should prove that the species on Si-cyos and Parietaria 

 also produce zoospores, the proportion would be still greater. Our Peronosporce 

 may be divided into two groups, those in which the ramification is pinnate and 

 those in which it is dichotomous. In each group there are species which close- 

 ly resemble one another, and one is tempted to ask how far the different forms 

 described are really specifically distinct. Of the pinnate group, although we 



