Moore : The study of winter buds 139 



crowded condition (figures 3, 4, 9, 21, 22). This stretching in the 

 apical part of the meristematic region causes no change in the size 



^.>^.. ^^^^^^ ..^ ^^.t^iig 



or in the external appearance of the buds under investigation, 

 although it becomes a measurable factor in the leaf buds of Sam- 

 biiats and of Pruniis^ species which more readily respond to the 

 continuous high temperatures of an unusually mild winter. 



Kiistersays that during the warm winter of 1899 leaf buds of 

 Acer platanoides showed not only a stretching of the cells but also 

 an addition of new tissue in the axils of the upper leaves. These 

 results must be seriously questioned, for his drawings of free-hand 

 sections do not give the accuracy of detail which the microtome 

 sections reveal. A careful search through many series of sections 

 proves conclusively that what Kiister called new tissues are the 

 basal parts of the petioles which partially encircle the young axis 

 of the bud (figures 31 and 32). 



All cells in the tissues of the winter buds are exceedingly small 

 and closely packed together. A pronounced stretching of the 

 tissue occurs in the following species during February: the inner 

 scale fundaments of Aesciihts Hippocastaniim increase in length 

 (figure 38); the rudimentary leaves oi Syrhiga vulgaris appear 

 larger (figure 10) ; the bud oi Philadelphiis^ which in its dormant 

 state is buried beneath the leaf scar, protrudes as a tiny bud 

 through the rift in the upper portion of the scar. 



The mean temperature for the month of March was exception- 

 ally low for that month (figure K), yet there are many evidences 

 that growth occurred. Liriodcndron and Acer show minute .cush- 

 ions of tissue which later develop into axillary buds (figures 5 

 and 12), In Alniis the cushions of tissue increase slightly in size 

 (figure 51). A change in the color of the Salix buds, a change 

 from a dull red to a more living ox\^, gives evidence that the life 



processes are more active; their interior structure also reveals 

 growth by the enlargement of parts at the growing tip (figure 

 23), and in the more deeply staining tissue at the leaf axils. 

 Buds of /7^(^-f/>///i-show no additional tissue but a general stretching 

 of all parts. These buds whichshow^a gradual but unmistakable 

 advance in interior structure through February and March undergo 

 rapid and vigorous growth in April when the leaf blades become 

 more or less expanded and free. 



