32 PH YCOM J XE TES 



P'amily I. Albuginaceae. 



1. Conidiophores club-shaped, formed under the epidennis of the host ; 



conidia formed in chains in white masses under the epidermis of the 



host. Albugo*. 



Conidiophores formed outside the epidermis of the host ; conidia formed 



singly, never in chains. 2. 



Family 2. Peronosporaceae. 



2. Conidia forming zoospores, or at least discharging their contents as a 



whole. 3. 



Conidia gemiinating with a primordial membrane. 6, 



3. Conidiophores simple up to the formation of the first conidia, later pro- 



ducing lateral branches and conidia. Phytophthora. 



Conidiophores with conidia-bearing branches, completely formed before 



the development of the oospores. 4. 



4. Conidiophore formed of a single hypha, which bears small uniform 



branches on the swollen end. Basidiophora. 



Conidiophores with branches rising fi-om different parts. 5. 



5. Oospores grown fast to the walls of the oogone. ScLEROSPORA. 

 OSspores lying free in the oogone. Plasmopara. 



6. Conidia with a papilla on the upper end through which the primitive 



hypha develops. Bremia. 



Conidia without papilla, germinating from the side. Peronospora. 



Of the above genera Albugo has six species. Besides A. 

 Candida^ growing on ^•arious Cruciferae, we have A. portidaccae 

 on purslane ; A. ipoinoeae-pandiiranae on sweet potatoes and 

 various species of Convolvulaceae ; A. tragopogoiiis on thistles, 

 salsify and a few other Compositae ; A. bliti on Aniaj^antus 

 widely distributed, and A. platcnsis on various Nyctaginaceae, 

 more or less common in New Mexico. 



PhytophtJiora has P. iiifestans already discussed on the potato, 

 and other Solanaceae, and P. pJiaseoH on Lima beans. Basidio- 

 phora has a single species on Erigero7t, Aster and Solidago. 

 Sclerospoi'a has a single species on various grasses. Plasmopa7'a 

 has P. viticola already discussed on various forms of native and cul- 

 tivated grapes, P. geranii on the wild geranium {G. Ca,roliniaimvi) , 



* Until recently more commonly known under the later name of Cystopus 

 candidus. 



