1881. ] Botany. 133 
are present in a pabulum, though in small quantity only, the mil- 
dew usually commences to be visible to the naked eye as minute 
yellow spots. These, as we have just said, may be caused by the 
growth of the mycelium, which in providing nourishment for 
itselfand for the subsequent fructification of the fungus, brings 
about a decomposition of the nitrogenous materials, and gives 
rise to crenic and other organic acids. Ata more advanced stage, 
humic and ulmic acids are produced, the fiber of the cloth becom- 
ing at the same time perceptibly more tender. It has been said 
that mildew may exist on the sizing only of a fabric. Weare in- 
clined to doubt this, for in our experience the mycelial threads 
have never been confined to the surface size alone, but could 
always be traced ramifying amongst the cotton filaments. If the 
size alone of a cloth were smitten with mildew, the cloth itself 
would not be tendered, unless the acids we have mentioned were 
a sufficient cause, which is not so. We believe it impossible for 
mildew to be present in such amount as to be clearly visible to 
the eye without a penetration of the mycelium to the textile sub- 
stratum, and should expect a suitable magnification and illumina- 
tion of the object to reveal the fact.” 
s to the colors of mildews, according to the authors, yellow 
patches on cloth are mostly due to the presence of crenic acid, 
although very rarely they proceed directly from the fungus, 
Penicillium sitophilum ; green mildew is nearly always due to the 
fructification of Penicillium crustaceum ; and dark-green or green- 
ish-gray mildew is owing to the fructification of a Penicillium or 
Aspergillus, or to the mycelium of a species of the Dematiei. 
Brown mildew may be due to the presence of apocrenic acid, or 
of one or more of many fungi. Red patches appear to be due to 
fungi; those mentioned by the authors being a species of Epicoc- 
cum, Aspergillus roseus, and Papulaspora sepedontoides. 
ALLEN’s CHARACE® AMERICAN® Exsiccat#.—We have had 
the pleasure of examining Part 1 of this important distribution of 
curious and little known plants. It includes three species of 
Nitella, and seven species and varieties of Chara. The specimens 
are of generous size, and are in excellent condition for study. 
The more interesting species are (Vitella intermedia, a new one, 
described by Nordstedt; JV. megacarpa, a new species now first 
described as such by Allen; Chara sejuncta A, Br., C. gymnopus 
A. Br, var. Mishauxii A. Br., a gigantic species, and C. hydropitys 
A. Br., var. sepientrionalis. The variety last named is described by 
Nordstedt, and is the same plant which Dr. Halsted described as _ 
a new species under the name of C. Roddinsii in the Proceedings 
of the Boston Society of Natural History, xx; 1879. Vétella 
megacarpa Allen, is the same as J. ztricata Ag., in Halsted’s 
paper; it is of very large size, and compared with the diminutive 
NV. tenuissima is a giant indeed. 2. 
The publication of sets of specimens like these cannot fail to 
