7 oo 
Journal of Agricultural Research voi. xxvii. No. 9 
of the species are described so vaguely or so briefly that almost any mem¬ 
ber of the genus could be placed within them. Many investigators, 
finding an Altemaria on a new host, have made a new species of it and 
published a brief description wholly inadequate for purposes of positive 
identification. 
Elliott (9) has done much toward the establishment of the generic 
limitations of Altemaria and has sorted out some of the species into 
groups. He states: “No final disposition of the present specific names of 
Altemaria and Macrosporium can be made without a study of authentic 
specimens of each species. Most of the descriptions are far from being 
complete or definite enough to permit their being used for this purpose.” 
Until such work as Elliott suggests is done, the identification of species 
of Altemaria must in most cases be quite uncertain. 
Elliott’s emended description of the genus is such that A . mali un¬ 
doubtedly belongs within it. His description is as follows: “Altemaria 
Nees. Conidiophores solitary or fasciculate, erect or subdecumbent, 
simple or branched, generally short, colored. Conidia muriform, often 
with few longitudinal septa, ovate, obclavate, or elongate, always with 
more or less definitely pointed apex, often long-beaked, colored, under 
favorable conditions forming chains. (Ex. A. tenuis , type of the genus.)” 
The writer has studied Altemaria mali as found growing in dead spots 
on apple leaves and as cultivated on artificial media. In addition, 
Altemaria tenuis , from Europe, and species isolated from the leaves of 
lilac, forsythia, and blackberry and from the fruits of apple, cranberry, 
and blueberry have been grown on artificial media and studied. 
All these forms, while resembling one another in many respects, revealed 
many points of difference. In some species the hyphae were almost 
colorless, forming a thin scarcely perceptible crust over the surface of a 
plate of corn-meal agar with an exceedingly scant production of conidia 
and no aerial hyphae. Others formed a dense, nearly black crust with 
a copious production of conidia and no aerial hyphae. Still others pro¬ 
duced a black crust with abundant conidial production at its surface and 
an abundance of more or less flocculent aerial mycelium or a greenish- 
gray aerial mycelium so dense as to form a thick carpetlike growth over 
the surface of the culture medium. A few produced an abundance of 
dirty white aerial hyphae with a very scant growth in the medium or 
along its surface and a very scant production of conidia. 
In the species studied the conidia conformed to the generic descrip¬ 
tion, that is, they were ovate, obclavate, or elongate. In most of these 
obclavate conidia predominated, but ovate conidia were found in cul¬ 
tures of all except one form which produced elongate forms exclusively. 
In the species producing practically no aerial hyphae, elongate conidia 
predominated. While the surfaces of the spores were usually smooth, 
in some forms verrucosity was quite common. An entire conidium or 
only a part of it often possessed a verrucose surface. If only a part of 
the conidial wall was verrucose, it was in a strip or band at right angles 
to the long axis of the conidium. Verrucosity or absence of verrucosity 
was not so much a difference between conidia as between chains of coni¬ 
dia, the conidia of individual chains usually being all verrucose or all 
smooth-walled. The presence or absence of verrucosity appears to be 
due to highly localized conditions of the immediate environment, if one 
may judge from selection experiments reported upon later in this paper. 
The conidia of all the species were produced in chains with the narrower 
end distal. De Bary (r), Jones (rr), Elliott (9), and many others found 
