SummaryThe chemical composition and distribution of storage nitrogen in young peach trees and the importance of this stored nitrogen for new growth were investigated. Young peach trees, which were grown in sand culture for two growing seasons, accumulated nitrogen in proportion to supply during the first year, and the results suggested that this stored nitrogen was utilized for new growth during the second growing season irrespective of the external nitrogen supply. Tree growth in early spring was significantly correlated with the level of storage nitrogen in tree tissues, but after November tree growth was markedly dependent upon the external nitrogen supply. If fertilizer nitrogen was not applied, the supply of storage nitrogen in tree tissues was exhausted by the end of November. Reaccumulation of storage nitrogen began in tree tissues in December and was rapid if the external nitrogen supply was high.Storage nitrogen in dormant trees consisted mainly of soluble organic nitrogen and free arginine was the principal constituent of this fraction. The level of arginine in woody tissues of the dormant trees was the most sensitive indicator of the nitrogen status of the trees.Approximately 60-80% of the storage nitrogen in dormant 2-year-old trees was found in root tissues, irrespective of the nitrogen treatment.

A detailed study has been made of the morphology of the spring.barley apex from shortly after germination to shortly before heading. The effects of 8-and 24-hr light periods and three levels of soil-moisture tension were examined with reference to the total number of primordia initiated on the main stem, the length of the apex, and the rate of spikelet development.For the environmental conditions explored it was found that the initiation of double ridges occurred when the apex was a particular length (0' 45 mm), and that the initiation of internode elongation, the appearance of stamen initials on the most advanced spikelet, and the cessation of primordia formation occurred concurrently.

Types, numbers, volumes, and weights of starch granules in the barley endosperm were measured at different times from anthesis to maturity. The formation of two types of granule was confirmed: the first (type A) was initiated until 15 days after anthesis; the second (type B) between 18 and 30 days. At maturity there were approximately 10 times as many type B granules as type A, although the latter made up 90 per cent. of the total granule volume. There was a linear relationship between starch granule and endosperm volume throughout kernel development, while the rate of increase in volume per unit granule volume was the same, irrespective of granule size, at anyone time. Starch weight increased as endosperm dry weight increased although the precise form of this relationship is in doubt. The interrelationships between starch granule weight and volume, and also endosperm dry weight and volume, suggest that both starch granules and endosperm increase in density during development.

The root growth of barley plants was examined at weekly intervals during the 5 weeks following emergence. The lengths of the separate components of the root system (prima.ry, secondary, tertiary, etc.) were determined, as well as the number of branches and the distances apart of these branches.

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