Experiment Station Record, Volume 92, January-June, 1945 Page: 27

19451 AGRICULTURAL BOTANY 27
Natural revegetation of abandoned plowed land in the mixed prairie association
of northeastern Colorado, D. F. COSTFLLO. (U. S. D. A.). (Ecology, 25
(1944), No. 3, pp. 312-326, illus. 5).-Plant succession under these conditions proceeds
through an initial stage characterized by Salsola kali tenuifolia, Amaranthus
retroflexus, Chenopodium album, or other annuals; a forb stage consisting of a
large variety of annual and perennial forbs and a few grasses; a short-lived perennial
grass stage in which Schedonardus paniculatus, Hordeum jubatum, Sporobolus
cryptandrus, or Sitanion hystrix are usually abundant; a stage marked by dense
stands of Aristida longisetac or A. pupurea; and the fully developed mixed prairie
association, consisting of a mixture of short grasses, midgrasses, forbs, and shrubs.
In relatively undisturbed successions, the initial stage lasts 2-5 yr., the forb stage
3-6, the short-lived perennial stage 4-10, and the Aristida stage 10-201 yr. The
transition to climax mixed prairie may require 10-20 yr. Drought cycles and wet
years retard or accelerate the rate of succession. Other factors markedly influencing
the rate of succession are topography, intensity and duration of cultivation preceding
abandonment, and grazing. Succession is accompanied by an increase in complexity
of the floristic composition. Influents of considerable importance include
kangaroo rats, jack rabbits, and harvester ants. The small mammals tend to reduce
seed production of the midgrasses. Ants probably affect the seed supply, and their
mounds provide a substratum for the entrance of short-grasses into the succession.
Wild rice in Minnesota, J. B. MOYLE J(Jo. Wildlife Mangt., 8 (1944), No. 3,
pp. 177-184).-The State contains over 15,000 acres of wild rice (Ziacnia aquatica)
growing in shallow lakes and along streams in the northern and central parts. This
native grain exhibits considerable variation in size and number of kernels per head
as well as in other characteristics; it tends to develop local strains. The crop, in
addition to its value for waterfowl, provides an average annual harvest of about
500,000 lb. of processed rice. Up to 2,500 persons-about a third of Indian bloodengage
in the harvesting, and the grain usually has an annual value of $100,000
to $400,000. On any stand the harvest averages failure 1 yr. in 4, the principal
cause being a high water level during May-June. Sufficient grain for reseeding is
usually produced in these years of harvest failure. The limited data available suggest
that often as little as a tenth of the crop on a stand is taken by hand harvesting,
most of the grain being left for waterfowl and reseeding. When total production,
calculated as processed rice, is below 300 lb. per acre, hand harvesting is usually
unprofitable; the average harvest in Minnesota is about 3040 lb. per acre. Wild
rice is more of an attraction than a staple food plant for waterfowl and shows
marked preference for certain habitat conditions; unless these conditions are supplied
,plantings are apt to fail.
The effect of vitamin B1 on the utilization of glucose by Melanospora destruens
Shear, L. E. HAWKER (Ann. Bot. [London], n. se., 8 (1944), No. 29, pp. 79-90,
illus. 1).-The presence of 10y aneurin (vitamin B1) per 100 cc. medium increased
the amount of glucose consumed per unit dry matter of mycelium by this fungus.
The extra sugar consumed was not stored in the mycelium, and there was no large
accumulation in the medium of metabolic products containing C, such as inositol,
bicarbonates, or organic acids. The 02 uptake, and therefore presumably the amount
of C respired, per unit dry weight of mycelium was increased by vitamin B1 sufficiently
to account for the extra glucose consumed; a similar result was obtained
with Phycomyces nitens. Previous accounts of the effects of growth substances
on respiration are summarized and discussed (45 references). A correlation between
high respiration rate and production of perithecia by M. destruens is shown.
Action de la thiamine sur le Phytophthora infestans (Mont.) de Bary,
A. PAYETTE and C. PERRAULT (Canad. Jour. Res., 22 (1944), No. 3, Sect. C., pp.