Mat 1891,] BOTANICAL SOCIETY OF EDINBURGH. 117 



ceded movement in the buds by from 17 to 40 days, but in the 

 two species of Pinus the start was nearly simultaneous. In 

 all the deciduous trees, on the other hand, the buds showed 

 signs of activity long before measurable girth- increase 

 began, the periods varying from 22 to 68 days. Fortunately 

 the proof is strongest in the most extreme cases. Thus, there 

 can be no question that the hard, brown buds of Ahies 

 Lovnana showed not the slightest change from their winter 

 state up to 19th May, whereas the girth-increase began 40 

 days earlier ; and there can be equally little doubt that the 

 buds of Cratccgus Oxyacantha threw off their covers in the 

 end of February, while girth-increase in it did not begin till 

 the 7th May. 



But as the very early start of the deciduous buds was 

 followed by a long period of slight movement, let us take 

 the opening of the buds as a more decided era. The 

 correlation of the start in girth-increase with this event is 

 somewhat different. In the four trees first on the list the 

 buds still have a start varying from 19 to 39 days, but in 

 the two elms girth-increase precedes the opening of the buds 

 by 10 days. 



General Conclusions. 



1. In certain species of Conifers a great retardation or 

 actual stoppage occurs in girth-increase in summer. This 

 was observed in Pinus sylvestris and Abies excelsa by Karl 

 Mischke in 1888 (Bot. Centralblatt, xliv. 2, 1890) by counting 

 under the microscope, at frequent intervals, the number of 

 cells produced from the cambium, and this " sehr aufialliges 

 factum " he was inclined to attribute to exceptional 

 meteorological conditions, — a conclusion which was natural, 

 as he was dealing with only two trees in a single season, 

 with an abnormal temperature and rainfall. My more 

 extended observations, however, lasting for three years, and 

 including 8 conifers of six species, leave little room for doubt 

 that the phenomenon is constant, at least in some species. 



2. Further observations are necessary to ascertain whether 

 the law is applicable to all conifers. My monthly observa- 

 tions on girth-increase do not lead to the belief that it is, as 

 Table VI. shows : — 



