CYLINDROSPORIUM ON STONE FRUITS 
fugally as the latter grows in diameter. This growth of the stroma is 
lateral, extending out between the epidermis and mesophyll of the 
leaf, and never turns up at the edges so as to resemble a pycnidial 
structure.^ The stroma which bears conidia lies under the epidermis 
on either surface of the leaf. When the conidia have accumulated 
in sufficient number the epidermis is broken and they appear usually 
as a whitish or yellowish white mass above the stroma. In P. serotina 
(more rarely in other species) the stiff cuticle prevents the formation 
of a large opening and the conidia are forced out in long tendrils.^ 
The conidia from all the host species are very similar. They are 
long, slender, curved or flexuous, and continuous or 1-3 septate.^ 
There are a few minor differences which are not very distinct, since 
the conidia vary considerably on each host. The conidia from plum 
leaves (all three species) were more constant than those from cherry 
leaves. Here they are blunt at the proximal end and taper gradually 
toward the apex, and they are mostly once septate. The largest spores 
found were from P. serotina and P. virginiana. On both species spores 
measuring 45-80^1 in length were found. On no other species were 
they found as long as Sofx. 
^ Septoria cerasina Peck (29th Report N. Y. State Mus. Nat. Hist. 48, 1878) 
the type material of which, through the kindness of Dr. Peck, I have had an oppor- 
tunity of examining, has a typical fruiting structure of this description (fig. 4). 
The same is true of the specimen distributed in "Fungi Americana" No. 747 as 
Septoria Ravenellii Thiim, which is apparently identical with S. cerasina Peck. 
This is not the case, however, with Septoria pruni Ellis, which Aderholdt (i) includes 
as a synomym of Cylindrosporium padi Karst. Here a distinct pycnidial structure 
surrounds the spores which shows it to be a true Septoria. This was not from type 
material, but from the specimen in Ellis' North America Fungi 1151 in the Cornell 
University herbarium. It is from the same collection which Aderholdt must have 
examined, though of course in such a large collection some leaves affected with 
Cylindrosporium might also be iiicluded. 
^ This accounts for Peck's (23) statement that S. cerasina differs from Cylindro- 
sporium padi (on P. domestica) in this character. 
^Aderholdt (i) says that the conidia are not truly septate but have false cross 
walls. He does not state how this was demonstrated. Pammel (22) says that the 
cross walls react to stains in exactly the same way that the side walls react, and this 
has been confirmed by my own studies. Haidenhain's iron alum haematoxylin 
Delafield's haematoxylin, and Flemming's triple stain all bring out the cross walls 
very distinctly. Very often also the cells become constricted at the cross walls 
upon germination; or the contents of one cell may be lost entirely without appar- 
ently affecting the rest of the conidium. 
