9 



(de Bary, 3, p. 228) that a saccharine secretion oozes out from 

 the conidia-bearing surface. This secretion, in which the 

 conidia are imbedded, is eagerly sought by insects, which neces- 

 sarily carry away large numbers of the conidia. A large 

 number of species of insects has been found by Stager (47, 48) 

 to visit ergot-infected grasses. Mercier (35) showed that the 

 spores w^ere not only carried mechanically on the surfaces of 

 the bodies of insects but that they were also found in their 

 excrement. This latter statement, however, has been ques- 

 tioned by Gain (13). 



Insects have been shown by various writers to carry rust 

 spores. Magnus (33) called attention to the fact that the 

 teleutospores of various species of Diorchidium, and especially 

 D. steudnerij are well adapted to insect transport on account 

 of the fact that they are set free in dew drops, or other 

 moisture, and are sticky. Klebahn (31) thinks that insects 

 play a part in the local dissemination of rusts in general. 

 This author also thinks that the bright color of some rusts 

 may attract insects. Falck (10) suggests the probability that 

 rust pycnospores are also distributed by insects, in the same 

 manner as the teleutospores. Johnson (26) has made a micro- 

 scopic examination of a large number of thrips found on wheat 

 florets. A large per cent, of the thrips was found to be carrying 

 spores; in one instance "five rust spores and three conidial 

 spores of imperfect fungi were observed attached to the 

 antennae and appendages of a single thrip." This writer is 

 of the opinion that the presence of rust spores between the 

 glumes of florets of wheat and the consequent rusting of the 

 heads which he observed, were due in part to the activities of 

 the thrips. 



Ludwig (32, p. 369) has pointed out the close similarity 

 between the spores of smut fungi and pollen grains. He calls 

 attention to the fact that those smut spores which have a 

 roughened cell wall are found on those parts of their hosts 

 which are regularly visited by insects. Such spores very 

 frequently develop in the anthers of insect pollinated flowers. 

 On the other hand, the smooth walled spores are more fre- 

 quently met with on those parts of plants where insects are 



