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Journal of Agricultural Research voi. xxvti, No. i© 
herbaria; while detailed study has been made on the morphology (2, 12) 
and cytology (26) of its development, on comparative spore measure¬ 
ments (27), and on the relation to the host attacked (2, 22 , 23). 
Since the genus was founded, nine other species have been described. 
Of these, Sclerospora macrospora Sacc. (18) > which includes 5 . krie- 
geriana Magn., according to Traverso (27), S. miscanthi T. Miyake (16), 
S. farlowii Griffiths (9), and 5 . magnusiana Sorokin (25), have been 
reported as yet only in the oosporic condition. The remaining five 
species are alike in that: First, their conidial phase is predominant and 
destructive, the oosporic being absent or rare; second, their conidia 
germinate invariably by hyphae; third, they occur in the oriental Tropics 
and on members of the tribes Maydeae and Andropogoneae. They are thus 
in contrast to the type species, 5 . graminicola ) which is destructive and 
predominant in its oosporic condition, which typically produces zoospores 
in conidium germination, and which is of world-wide distribution, 
mostly on members of the Paniceae. 
While investigating two of the conidial Sclerosporas of the Orient, 
namely, 5 . philippinensis and 5 . spontanea , species exceedingly de¬ 
structive to maize in the Philippine Islands, the writer (29, 30) found 
that in both, conidia were produced on the leaves of the infected plants 
only at night when they were covered with a layer of dew. On dewy 
nights, from about midnight to dawn, the innumerable successively 
emerging conidiophores formed a conspicuous and luxuriant growth of 
grayish down, and furnished abundant living material in all stages of 
development, quite different from the scanty remains, killed and de¬ 
formed by drying, that persisted for collection or study during the 
following day. This nocturnal conidiophore production proved to be a 
very fixed and characteristic process in 5 . philippinensis Weston and 
5 . spontanea Weston. Examination of the publications of other 
investigators suggested strongly that this condition holds also in the 
othfer conidial Sclerosporas of maize and related crops in the Orient, 
namely, 5 . javanica Palm (17) of Java, 5 . maydis (Rac.) Butl. (3) of 
India, and i>. sacchari T. Miyake ( 16) of Formosa. Indeed, in the case 
of the last species, which has been introduced recently into the Philippines 
(jj, 3i) y there is now no doubt that conidium production is nocturnal, 
as material collected at intervals during the night and sent to the writer 
through the cooperation of H. Atherton Lee, of the Bureau of Science in 
Manila, shows this to be true. 
PRODUCTION OF CONIDIA IN SCLEROSPORA GRAMINICOLA 
• 
Whether the type species, Sclerospora graminicola,' also produces its 
conidia only at night is a question that naturally presents itself, in 
view of the fact that this species differs in the several respects already 
noted from the conidial Sclerosporas of the Orient which show this 
peculiarity. Opportunity to investigate this point occurred while the 
writer was attending the summer conference of cereal pathologists at the 
University of Minnesota in 1920. On the grounds of the College of 
Agriculture, not too far from the plant pathology laboratory which Dean 
Freeman and Doctor Stakman very generously made available for night 
work, were found several plants of Setaria viridis (L.) Beauv. obviously 
infected with the conidial stage of Sclerospora graminicola . 
The fact that the tissue of these plants was pervaded extensively by 
vigorous mycelium of the parasite, and the leaf surface was marked by 
