54 
It is with difficulty that a twig can be kept in a moist chamber without 
this species making its appearance. 
I. Glceosporium Nervisequum, (Fckl.) Sacc. 
t 
The Platanus (sycamore) frequently exhibits an epidemic disease that 
is especially injurious to the young trees. The first manifestation of 
the malady is the wilting of the young leaves. Soon after they unfold, 
about the middle of May, brown spots make their appearance on any 
portiou, and extend along a vein, toward the base, over the leaf, and 
even on the pedicel, until the leaf finally falls off. Upon these dry places 
are small black dots just visible to the naked eye, and representing the 
gonidial form of a fungus probably belonging to the Pyrenomycetes. It 
has been seen in most cases on Platanus occidentalis.* Leveille, Fuckel, 
and Saccardo state that it also occurs on Platanus or l entails, but I have 
not been able to prove these statements. In addition to this, Fuckel 
refers to a form growing on the oak,f which he has distributed in his F. 
Khen. No. 428. * _ 
This fungus has been known for a long time. It was first described by 
Leveille as Hymenula platani in 1848, but it is surprising that neither he, 
Fuckel, or Saccardo mention its destructiveness. In his Symbolic, p. 
3G9, Fuckel cites it as Fusarvum nerviseqnum and gives an illustration of 
one of the spores. In the F. Khen. No. 427 it is called Labrella ? nervi- 
sequum , Fckl. Saccardo placed the fungus in the broader genus Glceo¬ 
sporium and adopted Fuckel\s specific name, since a Gloeosporium platani, 
(Mont.) already existed. It is therefore known as Gloeosporium nervi- 
sequum , (Fckl.) Sacc. 
If the infected areas are placed under a low magnifying power they 
show brown or black pustules which are elongated in form and most 
generally located in the angle formed by the vein and the leaf surface, 
but are also found on both these parts. Generally they occur upon the 
upper side of the leaf; much more rarely upon the lower. 
The structure of the fungus may be seen in a cross-section of one of 
these pustules (Fig. 1). The fungus destroys the walls between the epi¬ 
dermal cells, and the outer wall with the cuticle arches up until it bursts 
when the spores are ripe. The base of the pustule is lined with a pseudo- 
parenchymatic tissue composed of small ceils which may be called a 
stroma. From this arise numerous hyplne which penetrate the leaf, 
passing between the cells and completely destroying the leaf tissues. 
From the upper side of the stroma numerous hyplne or basidia grow 
out into the cavity of the pustule. These swell up and become club- 
shaped and cut off spores from the end. They are of unequal lengths, 
and the club-shaped swellings begin with the growth of the basidia. 
The spores are detached in great numbers; when the epidermis rupt¬ 
ures they exude in the form of a worm like, whitish-yellow mass. They 
are very irregular in shape, being mostly elliptical or pear-shaped, and 
* It lias been found in California on Z\ orient-all* by Markness. 
*} 
t Specimens on oak have been sent to the Department from Indiana. 
