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JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



that this must be so ; but I should like to add an illustration 

 which presents itself every spring, and always excites increasing 

 wonder. I allude to the remarkable growth -movements of the 

 shoots, especially of the leader. During the period of rapid 

 growth this may be observed particularly well in some species 

 of Abies in which the shoot bends from the vertical nearly or 

 quite to the horizontal, whilst its point is directed in the course 

 of a few hours to each point of the compass in succession. 

 Similarly the side-shoots are twisted as growth goes on. These 

 are growth-movements such as Darwin watched so carefully in 

 climbing plants and in root-tips, and which probably occur in some 

 degree in all plants, but which one would hardly expect to see in 

 so marked a degree in the stiff-looking shoots of the Conifers. 



These movements depend upon the circumstance that the 

 activity of growth and the fulness or turgescence of the cells of 

 the shoot, which is a necessary accompaniment, are not equal in 

 amount in all parts of the shoot at the same time, but are greater 

 at one time in one part, at another time elsev/here. Another 

 circumstance inducing these gyrations, which is frequently over- 

 looked, is the amount of resistance offered by certain parts of 

 the shoot itself. Thus the most active growth is at the base of 

 the shoot (centrifugal). The apex of the shoot is occupied by 

 cells which are smaller, and which are, moreover, checked in 

 their growth by the compression exercised by the more or less 

 tightly packed leaves and bud-scales which surround the tip of 

 the shoot. The tip of the shoot then grows more slowly than 

 the basal portions, and, acting as a check or curb, causes the 

 shoot to twist just as we may conceive the radicles to do in 

 consequence of the restrictions offered by the root-cap. 



The movements of the leaves are of a different nature, and 

 are very conspicuous in some species, as in Abies Veitcliii and 

 Picea ajanensis. By these movements the stomate-bearing sur- 

 face — whether it be, as is usual, the lower, or, as it is by exception, 

 the upper surface, as in Junipers and in Picea ajanensis — is 

 exposed to the heat and light of the sun, and the evaporation o 

 vapour is proportionately facilitated. 



Practical Illusteations. 



I do not advocate the comparative study of Conifers through- 

 out all the stages of their growth for purely scientific reasons. 



