Notes and Brief Articles 



341 



effusum t Morg., D. testaceum Pers., Didymium squamulosum 

 Fries, Fuligo septic a Gmel., Leo carpus fragilis Rost., Mucilago 

 spongiosa Morg., Physarum cinereum Pers., and P. sinuosum 

 Weinm. 



The insect transmission of diseases is treated at length in an 

 article of the greatest importance by F. V. Rand and W. D. Pierce 

 in Phytopathology for April, 1920. According to the authors, 

 the investigations of the past three decades have completely revo- 

 lutionized our view of the role of insect transmission in both plant 

 and animal diseases. Among the points to be studied are the fol- 

 lowing. It is necessary to determine on or in what part or parts 

 of the body the contagium is carried ; whether the transmission 

 is mechanical or biological ; how soon after taking up an infective 

 principle transmission is possible ; how long the insect remains 

 infective ; whether an infected larva may retain the contagium 

 through its metamorphosis ; whether the contagium can be trans- 

 mitted to the offspring, and if so, for how many generations ; 

 whether the offspring can transmit the disease at any stage of its 

 development; whether an infected insect remains infective after 

 a period of feeding on non-susceptible hosts ; and whether the 

 contagium winters over in the insect. The mere fact, however, 

 that the contagium of a disease is found in or on the body of an 

 insect should in no case be taken as final proof of an insect rela- 

 tion to transmission. In many diseases an inoculating needle, a 

 piece of wood, or anything which happens to come into contact 

 with the diseased tissues will carry upon it some of the contagium. 

 The final criterion, then, should be the actual transmission of the 

 disease under controlled conditions simulating as nearly as pos- 

 sible those found in nature. 



Artificial and insect transmission of sugar-cane mosaic is dis- 

 cussed by E. W. Brandes in a reprint from the Journal, of Agri- 

 cultural Research issued May 1, 1920. It is considered by the 

 author as proved that the cell sap of diseased plants is infectious 

 when introduced in the proper manner and that the disease can 

 be transmitted by insects. Just what insects are responsible for 



