THE FUNGI WHICH CAUSE PLANT DISEASE 323 



gives rise to a terminal group of elongate sporidia, these often 

 bearing secondary and even tertiary groups. 



The only species of this genus which occur on economic plants 

 are D. gossypii Lagerh.'^ on cotton in Ecuador and D. niesslii 

 de Toni (Niess) Schr. on Butomus. 



The following genera, which are usually referred doubtfully to 

 the Ustilaginales will be found under "Genera of Unknown Af- 

 finity" page 663. 



Graphiola Poit. on various palms. Schinzia Nag. on Solanum. 

 Bornetina M. & V. on Vitis. 



Protobasidii (p. 299) 



The three orders which belong to this group are characterized 

 by septate basidia. 



Key to Orders of Protobasidii 



Basidia with cross walls 

 Basidia arising from chlamydospores, 



Life cycle polymorphic. Parasites 1. Uredinales, p. 323. 



Basidia not arising from chlamydospores 

 . Not polymorphic. Gelatinous sapro- 

 phytes 2. Auriculariales, p. 392. 



Basidia with lengthwise partitions, gelat- 

 inous saprophytes 3. Tremellales. 



Uredinales "' "' **' "*• **• ^*^' "'*-"^' ^''^- "'-"'' * 



Small fungi, mostly microscopic, parasitic in the tissues of 

 ferns and seed plants. Mycelium much branched, septate, and 

 with haustoria. Spores borne in sori below the surface of the host, 

 or rarely single within the host. Sori naked, enclosed by peridia 

 or paraphyses, or embedded in a thin stroma. Spores of five mor- 

 phological sorts, not all present in every genus; (1) basidiospores, 

 minute, thin-walled, without surface sculpturing, (2) pycniospores, 

 small, smooth, of unknown function, (3) aeciospores, verrucosely 

 sculptured, borne in chains, (4) urediniospores, echinulately or 



♦Arthur's terminology involving the words pycnium, aecium, uredinium, 

 telium and derivatives from these words, will be followed in the treatment of 

 this order. 



