140 Moore : The study of winter buds 



In leaf buds which develop more slowly, as in Qiierciis^ 

 Hicoria^ Fagus^ Popidus^ and Tilia^ there is little evidence of 

 growth or stretchmg in the meristematic points or other local 

 areas from November to March inclusive. It seems probable that 

 growth entirely, or almost entirely, ceases for a time. A cyto- 

 logical and a physiological study of these parts as they occur 

 during the winter is required to verify this conclusion. 



Geleznoff (1851), a Russian investigator who studied the leaf 

 buds of Qiicrcus and Bctida in their winter condition, says: " All 

 buds make some advance in growth of new tissues and organs 

 from December to February even at continued temperatures of o 

 and less." It is possible this report of the organization of new 

 parts at such temperatures is the result of incorrect observations of 

 unlike buds, for plant physiologists hold that the growth and the 

 construction of new organs at temperatures below 0° is impossible 

 (Davenport, 1897). 



In late March and early April the buds of Qiiercus, Hicoria, 

 and Fagits begin a general swelling which becomes noticeable in 

 a lengthening of the internodes and a more crowded condition of 

 the meristematic point. Betida, Popuhis, and Tilia remain dor- 

 mant for a longer time. Sections of the last two species indicate 

 changes by the i6th of April in the general length of scale or leaf 

 fundaments, and irregularities in the outline of the meristematic 

 surface (figures 26 and 29). Aside from the stretching of cells, 

 the outline of the buds of Bctula remains the same, but in the 

 region of the leaf axils the tissue becomes more deeply staining 

 than heretofore. On April 16 the leaf buds of Picea and Rhodo- 

 dc7idro7i appear as in the preceding months of the rest period 



FIGURES 40- 



Picea 



alteration In the papilla-like leaves which from now on assume 

 rapidly their needle-shaped character. No change, up to this 

 time, is visible in the leaf buds of Rhododendron. 



Sum m ar y 



In some species the full number of leaves that unfold in the 

 spring exists at the beginning of winter. In other species, the 

 majority of leaves are present at this time and additions occur at 

 the time of unfolding. The terminal and axillary buds of the next 



