Regional Spread of Moisture in the Wood 
of Trees. 
II.—Moisture-Spread in a Graft-Region. 
BY 
WILLIAM GRANT CRAIB, M.A., 
Regius Professor of Botany in the University of Aberdeen. 
With Plate CLXV. 
AN earlier paper * summarised the results of experiments on 
the spread of moisture in the wood of deciduous trees through- 
out the winter and early spring. The moisture present in each 
of the wood sections examined was expressed in terms of the 
percentage of the dry weight of the sections. In other words, 
the percentage represented the absolute amount of moisture 
present in 100 grms. (dry weight) of the wood of each particular 
section. This method of calculation has been objected to + on 
the grounds that a variable factor—specific gravity —is 
involved. I admit that an ideal result to have achieved 
would have been the separate estimation of the water of imbibi- 
tion and the physiologically available or free water per unit 
volume. 
At the commencement of the investigations various schemes 
were formulated for the purpose of arriving at definite conclusions 
along these lines. Every such theoretical scheme was in its 
turn abandoned when the practical details were considered. 
Some of the schemes involved, for example, the accurate 
determination of the volume of small, irregularly shaped pieces 
of dry wood—a process which would almost certainly lead to 
the introduction of errors. Other schemes, where accurate 
volumetric calculations were unnecessary, postulated very true 
cutting of the wood, so that all the ultimate sections should be 
of absolutely uniform dimensions and consequently of equal 
volume. The necessity for this accurate cutting of the sections 
militated against such a course of procedure. But. a still 
greater objection, to my mind, was the seme neglect of 
* Craib in Notes Roy. Bot. Gard. Edin., xi, p. 1 (1918 
+ Groom in Trans. Roy. Scot. Arb. Soc., xxxiii, p. ie (1919). 
[Notes, R. , Edin., No. LEX, May 1920.] ; A 
wt. a Ral & Co., ri Gp. 10, 
