214 THE AMERICAN NATURALIST. -[VoL: XXXIII. 
Dr. E. A. Burt: Zhe Formation and Structure of the Dissepiment 
of Porothelium. — The author traced the development of the fructifi- 
cations of Porothelium fimbriatum Pers. from their origin as papille, 
through the pore, to the tube stage, in the latter stage contrasting 
the structure of the dissepiment where the tubes are closely crowded 
together with its*structure where they are more scattered. 
This fungus occurs as a thin, closely adhering layer on dead limbs, 
etc. The papille are solid throughout their early history. Theydevelop 
into pores by the more rapid growth of some parts than of others. In 
some species, as P. friesii, the papillz are buried; in others, regarded 
as higher in rank, the papillae are buried only in early stages of 
growth. 
Dr. Erwin F. SMITH : Gelatin Culture Media. — By means of a 
chart, photographs, and paintings the author called attention to the 
diverse and confusing results different individuals working with the 
same organism might reach with gelatin culture media. Our knowl- 
edge of this very useful medium has increased greatly in recent years. 
The best paper in English is by Geo. S. Fuller, “ On the Proper Reac- 
tion of Nutrient Media for Bacterial Cultivation,” Journal of the Am. 
Public Health Association, October, 1895, Concord, N. H. The most 
confusing things are: (1) the fact that gelatin which reacts neutral 
or moderately alkaline to litmus is still acid to phenolphthalein and 
often exerts a restraining influence on bacteria, especially certain 
parasites ; and (2) the fact that grape sugar or cane sugar in gelatin, 
while stimulating growth, often entirely prevents liquefaction, so that 
one may be dealing with a liquefying organism without knowing it. 
Some liquefiers are more sensitive than others, and it is not yet known 
how small an amount of sugar will restrain the most sensitive forms. 
All gelatin media should be rendered neutral to phenolphthalein, 
and it would be well, for the present at least, to use beef broth free 
from muscle sugar in making gelatin. Possibly the restraining influ- 
ence of sugar may also be of some use in making gelatin plate cul- 
tures of slow-growing forms which are mixed with rapid liquefiers, 
and which under ordinary circumstances run over and spoil the plate 
before the desired form has been able to grow. 
All gelatin media should be titrated against », or 4; normal 
caustic soda, and then the desired amount of acid or alkali added in 
the form of double normal solutions so as not to much disturb the 
proportion of fluids and solids. The melting point depends on the 
amount of gelatin added, the length of the steamings, and the amount 
