Treesearch

Vacuum-drying, followed by storage in vacuo or in an inert gas, is effective for storing pollen of many species. It permits storage at room environments without rigid controls of either temperature or humidity, an advantage that becomes paramount during long-distance transfers of pollen when critical storage conditions are impossible to maintain. In the study reported here, the objectives were to learn if vacuum storage is effective for yellow-poplar (Liriodendron tulipifera L.) pollen and to determine optimum rehydration conditions.

The study of internal seed structure by radiography requires techniques which will give good definition. To establish the best procedures, we conducted a series of experiments in which we manipulated the principal controllable variables affecting the quality of X-radiographs: namely, focus-to-film distance, film speed (grain), exposure time, kilovoltage, and milliamperage. The results presented here will eliminate the need for repetition by others interested in moving directly to research applications of X-radiography. A few examples will illustrate the interpretation of detail and perhaps...

Forest genetics is the study of variation and heritability in forest trees. It is concerned with similarities and differences of various traits between related trees and their transmittance to the next generation.

Jack pine (Pinus banksiana Lamb.) is one of the major pulpwood producing species in the Lake States. It is found on a variety of sites, but its outstanding characteristic is its ability to make early rapid growth on dry sandy soils.

Attempts are continually being made to reduce the time between generations in forest trees through flower induction and stimulation studies and by selection for precocious flowering,

When the Kellogg Forest was established in 1932, 90 percent of the farmland in the locality was idle. The original tree cover had been oak-hickory on the upland areas and basswood, white ash, American elm, and black cherry on the lower, more fertile areas. Agricultural activities had begun between 1830 and 1850. Since then, continued cropping had resulted in severe erosion and eventual abandonment of most of the farms.

In spite of care taken in the selection of site and experimental design of provenance experiments, site heterogenity within the experimental area may be more complex than was anticipated when the experiment was established. The present paper describes a problem of this nature encountered in a red pine (Pinus resinosa Ait.) provenance experiment at the Petawawa Forest Experiment Station. An appropriate design for minimizing this problem is proposed.

The concentration of monoterpenes in Pinus monticola Dougl. has been shown to be genetically controlled (Hanover, in preparation). Genetic control of terpene concentration has been implied, also, from analyses of parents or interspecies hybrids in other species (Bannister et al. 1959; Williams and Bannister 1962; Smith 1964, and Forde 1964). Evidence that genes regulate the formation of plant terpenes has stimulated the use of the terpenes as an aid in population studies. Bannister et al. (1962) showed significant variation in α-pinene and β-pinene between three populations of Pinus...

Heterozygosity appears necessary to maintain fitness in many plant populations, and mechanisms favoring or enforcing cross pollination have evolved. Most important among the latter are dioecism and incompatibility.

In the West foresters have had considerable difficulty in reforesting south-facing slopes. We considered this problem when we selected plus-trees for the first Douglas-fir seed orchard in Region 6. We were, however, faced with the need to answer such questions as these: (1) Should we try to produce seed inherently suited for south slopes? (2) If so, should we strive to get seed primarily of high germinative energy, or is high germinative capacity an adequate indication of suitability? Before we can select for either of these traits we need to know how they are inherited. As part of a...