proceedings: botanical society 43 



to be either alternative or Mendelian. These resuUs were advanced 

 as evidence against the hypothesis that maize has originated by muta- 

 tion from teosinte. A summary of the evidence to date was held to 

 support the view that t(>osinte and the unknown ancestor of maize 

 had evolved by gradual changes along divergent lines and that the 

 divergence took place before the separation of the Maydeae and the 

 Andropogoneae. 



Evidence was presented for believing that the Maydeae and Andro- 

 pogoneae were closely related and should not be considered as separate 

 tribes. It was urged that a recognition of the close relationship of 

 these two groups was of practical importance in the study of maize 

 diseases and as a guide in establishing quarantine regulations. 



W. H. Weston: The downy mildews of maize, their origin and distri- 

 bution. During the past twentj^ years considerable alarm has been 

 occasioned by several serious downy mildews which have appeared on 

 maize and its relatives in the eastern tropics. Peronospora Maydis 

 Rac. has been very destructive to maize in Java, Madoorah, and Atjeh 

 since 1892; and although Euchlaena has so far proven immune, crosses 

 of this plant with maize are extremely susceptible. Sclerospora sac- 

 chari Miy. was reported in 1911 as causing serious injury to maize 

 and sugar cane, and capable of inoculation onto Euchlaena, in For- 

 mosa; and was later found also in Queensland and the Fiji Islands. 

 Sclerospora Maydis (Rac.) But. appeared on maize in India about 

 1913; and in 1916 a species of Sclerospora, possibly identical with this, 

 was found to be destroying the maize crop in certain parts of the Philip- 

 pines. Since these parasites are unknown in the Americas where 

 maize originated, it is probabl^ they have spread to maize from some 

 of the several related grasses native to the Orient. To prevent the 

 tremendous loss that would undoubtedly follow the introduction of 

 these diseases into the United States, the importation of maize and 

 its relatives from infected countries has been prohibited. 



G. R. Lyman: Plant Disease Survey ivork on the Physoderma disease 

 of maize. This disease was first found in this country by Barrett at 

 Urbana, Illinois, in 1912. It was first reported as of economic impor- 

 tance by Barre in South Carolina in 1914. During the next two years, 

 the disease was found to be prevalent in North and South Carolina, 

 Georgia, Florida, Alabama, and Mississippi. In 1917, it was also found 

 generally distributed in Tennessee. 



In September of this year, the Plant Disease Survey put twelve 

 scouts into the field to act in cooperation with the Office of Cereal 

 Investigations, Bureau of Plant Industry. In addition to the states 

 named, the disease was found to be prevalent in eastern Virginia, 

 Kentucky, southern Illinois, southeastern Missouri, Arkansas, and 

 Louisiana, and to be sparsely present as far north as New Jersey, 

 southern Minnesota, and South Dakota, and as far west as central 

 Nebraska and central Texas. It has evidently spread as far as cli- 

 matic limitations will permit its development, being inhibited by cold 

 weather in the North and by lack of moisture in the West. 



An intensive study was made of selected regions in the South Atlan- 



