Observations made over the past 5 years suggest that the most recent needles of red spruce (Picearubens Sarg.) in the Green Mountains of Vermont, U.S.A., are prone to browning and loss owing to cold stress and (or) winter desiccation. Particularly severe events occurred in the winters of 1981 and 1984 and the latter event was observed in detail. On many trees in all size classes, a large proportion of the 1983 needles turned reddish-brown between late February and early April, 1984. This pattern of discoloration and subsequent defoliation, which appears to be repeated periodically, can account for the visual symptoms of declining red spruce in the montane forests of the northeastern United States. A predisposition to winter damage appears to be a component of the decline and could result from natural or possibly anthropogenic factors.

We report four patients with a progressive myoclonic ataxic syndrome and associated coeliac disease. The onset of the neurological syndrome followed the gastrointestinal and other manifestations of coeliac disease while on a gluten-free diet, in the absence of overt features of malabsorption or nutritional deficiency. The condition progressed despite strict adherence to diet. The neurological syndrome was dominated by action and stimulus sensitive myoclonus of cortical origin with mild ataxia and infrequent seizures. Plasmapharesis and immunosuppressive treatment were tried in two patients but were not beneficial. Post-mortem examination of the brain in one case showed selective symmetrical atrophy of the cerebellar hemispheres with Purkinje cell loss and Bergmann astrocytosis, and with preservation of the cerebral hemispheres and brainstem. Coeliac disease should be considered in the differential diagnosis of all patients presenting with a progressive myoclonic ataxic syndrome.

Sapling sugar maple (Acersaccharum Marsh.) trees were defoliated artificially at 10-day intervals beginning May 27 and ending August 5, 1981. Refoliation, terminal bud and shoot development, and xylem starch and sap sugar concentration were observed in defoliated and control trees. All defoliated trees refoliated, but decreasingly with later defoliation. Defoliation caused an acceleration in the rate of primordia initiation in terminal shoot apices. After early season defoliations, the developing buds in the axils of the removed leaves abscissed, but axillary and terminal buds on the refoliated terminal shoots survived through winter. In late season defoliation, most buds of refoliated shoots did not survive and the next year's growth depended on axillary buds formed prior to defoliation. Thus, when progressing from early to late defoliations, the next year's shoot growth depended decreasingly on the last-formed and increasingly on the first-formed portions of the previous year's shoot. Early October starch concentration in xylem decreased with later defoliation and was nearly absent in shoots and roots of trees defoliated in late July. There was not, however, a corresponding decrease in sap sugar concentration. Mortality occurred only in late defoliated trees and was associated with starch depletion.

Cytohistology and the development and morphogenesis of sugar maple (Acersaccharum Marsh.) shoots were studied. Three types were recognized: short shoots, long shoots entirely preformed in the bud (Epf long), and long shoots partially preformed in the bud (heterophyllous). The three shoot types varied not only in the size and number of internodes and leaves but also in the development of terminal buds. Terminal bud formation was delayed in heterophyllous shoots but because of a shorter plastochron, which extended later into the growing season, the terminal apices of these shoots were able to annually produce more primordia than in other shoot types. The beginning of embryonic shoot formation, however, began about the same time (late July) for all shoot types.

White spruce trees (Picea glauca (Moench) Voss) producing annually the same number of tracheids had a much shorter season for cambial activity in Alaska (65° N) than in New England (43° N). We counted the number of potential dividing cells in the cambial zone (NCZ) and estimated the rate of cell division by determining the percentage of cambial zone cells in mitosis (MI) for trees of different vigor (annual tracheid production) from each region during the early summer period of relatively constant mitotic activity. Within each region, NCZ was dependent on tree vigor and MI was independent of tree vigor. Rate of tracheid production was higher in Alaskan trees because of their higher rate of cell division (higher MI).