1897 ] BRIEFER ARTICLES 6 F fe 
on slowly, and there is no danger that the material will become too 
hard and dry if it should be overlooked for several hours beyond the 
usual time required for thickening. Where large trays are needed, I 
have several times employed Petrie dishes with success. 
The material is thus ready for use on the shortest notice, and a 
sufficient amount for several years. When it is to be used the assis- 
tant cuts out an object in a block of collodion of convenient size, 
places it in the jaws of the microtome properly oriented, sections it, 
fixes a few sections to the glass slip with ether and alcohol, and the 
preparation is then handed to the student, or the student may do the 
sectioning for himself. Stains and after treatment may be used at 
discretion, and when the preparation is ready for observation and 
study the student has a permanent one which can be of use afterwards 
for reference or for demonstrations. I have large quantities of mater- 
ial stored in this way in collodion, some of which has been in this con- 
dition for over two years, and the sections this year show that it is in 
as good condition apparently as when first prepared. In order to 
show how far the method may be extended with success I will give 
here a list of the things imbedded in collodion which I have stored in 
greater or lesser quantity now in the laboratory, usually a sufficient 
amount to last for from five to ten years, and in some cases for a 
longer period. 
Fi ungt.— Olpidiopsis saprolegniz, Synchitrium decipiens, Empusa 
gtylli, Cystopus candidus, Peronospora alsinearum (conidial stage, 
Cogonia, and oospores), P. parasitica (same), P. effusa, Plasmopara 
obducens, P. halstedii, P. geranii, Ustilago zee, Doassansia opaca, D. 
martinoffiana, Pilacre petersii (from dried material), Crucibulum vul- 
Sare, Cyathus striatus, Collybia radicata, Coprinus micaceus, C. 
atramentarius, Puccinia pimpinella (three stages), Puccinia podophylli 
{two stages), P. asteris, P. orbicula, P. anemones-virginiane, P. xanthii, 
P. circeze, P. peckiana (caeoma and spermagonial stage), Uromyces 
caladii, Phragmidium gracilis (aecidial stage), Phragmidium sp. (aecid- 
lal stage), Gymnosporangium macropus, Roestelia on Amelanchier 
fruit, Melampsora farinosa, Aecidium clematidis, Ae. sambuci, Ae. 
impatientis, Ae. compositarum, Ae. grossulariae, Ae. podophylli, Mag- 
_ Rusiella potentillae, Morchella conica, Discina warneri, Herpotrichia 
_ keitii, Xylaria polymorpha, Entomosporium maculatum. => 
__-- Aége.—Fucus vesiculosus, Laminaria saccharina, Leathesia diffor- 
____ _Muls, Mesogloea divaricata, Nemalion multifidum, Dasya elegans, Chon- 
