250 PHYSIOLOGICAL BOTANY. 



the author measured the circumference of some trees, 

 which were about eight years old and in an active state 

 of growth,, at various periods from the commencement to 

 the end of the vegetating season, and calculated the 

 mean daily increase in the circumference of the stem for 

 each of these intervals of time. The trees were, Gymno- 

 cladus Canadensis, Gleditschia macracantlia, Tilia argentea, 

 Populus Grceca, Pavia lutea, and Morus alba. A table 

 of the increments is added. The following details are 

 selected from the author's remarks upon his experiments : 

 On the 22d of June the terminal buds of Pavia lutca 

 were already formed, but the lateral growth, instead of 

 ceasing, from the above period to the 22d of August, 

 somewhat increased; it then diminished to a small amount. 

 From the 2d of March to the 22d of June, hence before 

 the development of the terminal buds, the circumference 

 of the stem increased 11 '8 millimeters ; from the 22d of 

 June to the end of the year 16*2 millimeters; so that 

 by far the greater proportion of the increase occurred 

 during that period in which no leaves were developed. 

 The same was found to be the case, although less 

 strikingly, in Gleditschia and Gymnocladus. Hence the 

 author draws the conclusion, that these observations are 

 directly opposed to the theory of Petit-Thouars. Valuable 

 as they are in themselves, the adherents of Petit-Thouars 

 will not rest satisfied with them, but will object that the 

 roots of the buds, between the bark and the stem, which 

 cause the lateral expansion of the stem, would be small 

 and delicate at the commencement, but that they increased 

 with the activity of the leaves, and in this manner aug- 

 mented the thickness of the stem. The author adds, 

 that the circumference of the stem also increased, although 

 to a small extent only, when the buds began to enlarge 

 and expand. Hence he thinks that nutritive matter, 

 prepared the preceding year, is applied to the first ex- 

 pansion of the stem in the spring, without the leaves 

 preparing it. Why not ? Although it appears determined 

 by numerous experiments, that the leaves serve for the 



