32 PHYCOMYCETES 



Family I. Albuginaceae. 



1. Conidiophores club-shaped, formed under the epidermis 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 germinating 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 from different parts. 5- 



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

 Oospores 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 various Cruciferae, we have A. portulaccac 

 on purslane ; A. iponweae-panduranae on sweet potatoes and 

 various species of Convolvulaceae ; A. tragopogonis on thistles, 

 salsify and a few other Compositae ; A. bliti on Amarantiis 

 widely distributed, and A. platcnsis on various Nyctaginaceae, 

 more or less common in New Mexico. 



PhytophtJiora has P. infestans already discussed on the potato, 

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

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

 Sclerospora has a single species on various grasses. Plasnwpara 

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

 tivated grapes, P. geranii on the wild geranium (G. Carolinianum), 



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

 candidus. 



