No. 387.] PLANT MORPHOLOGY AND PHYSIOLOGY. 215 
of acid or alkali added. All of these disturbing influences should be 
taken into account. The per cent of gelatin used and the melting 
point of the prepared media should always be stated. 
Working with gelatin of varying grades of acidity and alkalinity, pre- 
pared according to Fuller’s scale, e.g., with + 50 + 40 + 30 + 20+ 10. 
o — 10 — 20 — 30 — 40 — 50, with interpolations and extension of 
the scale, if necessary, it is possible to obtain curves of growth de- 
cidedly different for different species, even those which are morpho- 
logically much alike and which behave the same on nutrient agar. 
On this scale the + signs indicate acidity and the — signs alkalinity, 
and the figures denote, per liter of nutrient gelatin, the number of 
cubic centimeters of the normal acid or alkali which would have to 
be added to render the medium exactly neutral to phenolphthalein. 
The litmus neutral point of gelatin is approximately + 25 of this 
scale. The varying behavior of Pseudomonas campestris in the same 
gelatin with different quantities of caustic soda is shown on the 
accompanying plate. 
Pror. CHARLES E. Bessey: Relative Infreguence of Fungi upon 
the Trans-Missourt Plains and the Adjacent Foothills of the Rocky 
Mountain Region. — A study of the fungus flora of the Trans-Mis- 
souri Plains, extending over a period of fourteen years, has shown 
that while the number of species is large the number of individuals 
is relatively small. This is in marked contrast to the flowering 
plants, where the number of individuals is relatively high as com- 
pared with the number of species, especially in the herbaceous 
groups. 
Of the principal groups of fungi, the Phycomycetes are usually 
quite infrequent, appearing in considerable numbers in wet years 
only ; the Perisporiacez are, likewise, not usually abundant, although 
occasionally becoming very abundant, as with the Phycomycetes : 
the Pyrenomycetez are numerous as to species, but ordinarily in- 
frequent as to individuals, with, however, some marked exceptions, 
as the ergot of Agropyron and Elymus (C/aviceps spp.) ; the Disco- 
mycetez are rare, excepting in the most favorable of seasons; the 
Uredinez are usually abundant, although the number of species is 
not exceptionally large; the Ustilagineze are not numerous in species 
nor commonly abundant in individuals, excepting for three or four 
which affect the cultivated cereals ; of the “ Fungi Imperfecti” the 
number of species is relatively large, while again the individuals are 
relatively infrequent. 
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