1154 



MANUAL OF DETERMINATIVE BACTERIOLOGY 



2. Morsus reprimens .spec. nov. From 

 Latin reprimere, to restrain, check, or 

 curb, in reference to the inhibiting effect 

 on growth of the host plant, tobacco. 



Common name : Tobacco yellow-dwarf 

 virus. 



Hosts: SOLAN ACE AE—Nicoiiana 

 tabacum L., tobacco; A'", rustica L., In- 

 dian tobacco; N. trigonophylla Dun. 

 Experimentally, also N. glauca Grah. 

 (symptomless) and N. glutinosa L. 



Geographical distribution : Australia 

 (Victoria, New South Wales, South Aus- 

 tralia, and southern Queensland). 



Induced disease : In tobacco, internodes 

 of stem shortened, leaves small; down- 

 ward bending of tips and rolling under of 

 margins of young apical leaves; young 

 leaves darker than normal at first, 

 bunched, later appear ribbed; leaves be- 

 come yellow-green, pale first between 

 veins; old leaves rugose, thickened, later 

 savoyed. Root system small, roots 

 slightly brown externally and in the re- 

 gion of the phloem. Affected plants may 

 survive the winter and show diseased new 

 growth in the spring. 



Transmission: By grafting and bud- 

 ding. By nymphs and adults of the leaf- 



hopper Thamnoiettix argentata (Evans) 

 (CICADELLIDAE). 



Literature : Dickson, Australia, Coun- 

 cil Sci. Indust. Res., Pamphlet 14, 1929, 

 22; Hill, Australia, Journal of the Coun- 

 cil Sci. Indust. Res., 10, 1937, 228-230; 

 14, 1941, 181-186; 16, 1942, 13-25. 



3. Morsus ulmi spec. nov. From Latin 

 ulmus , ehn. 



Common name : Elm phloem-necrosis 

 virus. 



Host : U RT IC ACE AE— Ulmus ameri- 

 cana L., American elm. 



Geographical distribution : United 

 States (Ohio, Indiana, Illinois, Missouri, 

 Tennessee, Kentucky, and West Vir- 

 ginia). 



Induced disease: In elm, gradual de- 

 cline over a period of 12 to 18 months 

 before death or sudden wilt, drying 

 of leaves, and death within 3 to 4 weeks. 

 All ages susceptible, from seedling to 

 large tree. 



Transmission : By patch grafting. Not 

 by inoculation of expressed juice. 



Literature : Leach and Valleau, U. S. 

 Dept. Agr., Plant Dis. Rept., 23, 1939, 

 300-301; Swingle, Phytopath., 30, 1940, 

 23. 



Genus IV. Aureogenus Black. 

 (Proc. Am. Philos. Soc, 88, 1944, 141.) 



Viruses of the Yellow-Dwarf Group, inducing diseases characterized by yellowing 

 without typical mosaic-type mottling. Vectors agallian leafhoppers (CICADELLI- 

 DAE). Generic name from Latin aureus, yellow or golden, and genus, group. 



The type species is Aureogenus vastans (Holmes) Black. 



Key to the species of genus Aureogenus. 



I. Mechanically transmissible in some hosts by rubbing methods'of inoculation. 

 Not producing enlarged veins or club-leaf in clover. 



1. Aureogenus vastans. 



II. Not known to be transmissible by rubbing methods of inoculation. 



A. Producing enlarged veins in clover. 



2. Aureogenus magnivena. 



B. Producing club-leaf in clover. 



3. Aureogenus clavifolium. 



