448 
JOHN A. ELLIOTT 
One species, A. cucurbitae'^'^ Let. & Roum., Fungi Sel. Ex., Roum., 
3694, did not afford enough material for judgment. 
The above study of exsiccati and descriptions brings not only 
species into question but genera as well, since in all but the first and 
second of the above groups both Alternaria and Macrosporium are 
included in groups as morphologically similar. 
IV. EXPERIMENTAL RESULTS 
Cultures of Alternaria and Macrosporium and material upon which 
either was growing were secured from many sources.^ Of eighty cul- 
tures thus obtained all but two produced chains of spores regularly 
on artificial media and accordingly belonged in the genus Alternaria. 
All of these had clavate, elongate or ovate, more or less pointed spores. 
The two which did not ordinarily produce chains of spores had glob- 
ular or sarcinaeform conidia. One of these very rarely produced 
chains of two spores, in which cases the bottom spore was pointed. 
Eleven of the cultures were selected as representative of all the forms 
present and as most suitable for extensive study. These eleven cul- 
tures also represented all of the morphological forms found in exsiccati. 
They were: Alternaria solani (E. & M.) J. & G., isolated from blighted 
potato leaves {Solanum tuberosum L.) ; A. solani isolated from Datura 
leaf spot {Datura stramonium L.) ; A. brassicae var. nigrescens Peglion, 
isolated from blighted cantaloupe leaves {Cucumis melo L.) ; A. bras- 
EXPLANATION OF GRAPHS i TO 9 
The measurements of spores are indicated in microns by the base line, each 
space representing one fx. The frequency is indicated on the perpendicular lines, 
each space representing one spore. Measurements are at intervals of 2.4 ^^ except 
in the case of the narrower spores where the width is taken at intervals of 1.2 /z. 
The following letters are used to indicate the host and media: A, natural host; 
B, bean agar, 30°; C, bean agar, 10°; D, bean agar, + 20 Fuller's scale; E, bean agar, 
— 20 Fuller's scale; F, synthetic agar; G, synthetic agar minus glucose; H, synthetic 
agar with double amount of glucose; /, synthetic agar with double amount of as- 
paragin; /, synthetic agar without asparagin; K, leached agar. 
The most striking facts to be observed are: general reduction in size of spores on 
the synthetic agars (7^ to J), over that on bean agars {B to E). Relative constancy 
of species given in graphs 2, 4, 5, and 6 over those given in graphs 3, 7, 8, and 9. 
Increase in size of spores at lower temperature (Graphs 7 and 9; C). Extreme range 
of variation in size of larger spores (graphs i, 2, 3, 8 and 9). 
^ Cultures or material was received from J.J. Davis, L. R. Jones, B. F. Lutman, 
W. G. Sackett, S. M. Tracy, H. T. Gussow, E. C. Stakman, G. P. Clinton, M. T. 
Cook, G. F. Atkinson, B. D. Halsted, I. M. Lewis, C. W. Edgerton, C. R. Orton, 
B. B. Higgins, J. W. Eastham, Miss Jean Maclnnes, G. L. Peltier, F. C. Stewart.* 
