32 SPIRAL AND DISTICHOUS BUDS [CH. 



the twig, and this in such a way that if, starting from 

 the lowermost bud, such a spiral line passes through three 

 or five other bud-insertions as it completes its course 

 round the twig to the next bud vertically above the one 

 started from, then there will be three or five vertical 

 ranks of buds respectively. In the case of the distichous, 

 or two-ranked, arrangement, it is also true that a spiral 

 line carried once round the stem from a lower bud to the 

 bud next vertically above it passes two buds, and these 

 facts can be expressed in a sort of shorthand. 



Thus \ implies that the spiral line drawn as above 

 passes once round the stem and passes two buds in its 

 course ; \ signifies that the spiral line in one complete 

 journey round the stem from bud to bud passes three 

 buds; and f tells us that the spiral passes five buds in 

 its course to the next bud vertically above the one we 

 start from, but has to pass twice round the stem to do 

 it. And similarly with other arrangements, but for our 

 purposes it suffices to regard all cases of alternate buds as 

 coming under two heads the distichous or two-ranked 

 arrangement, and spiral arrangements other than that. 



Buds are obviously distichous on the longer twigs of 

 the following : 



Elms Hazel Lime 



Beech Hornbeam Chestnut. 

 Less conspicuously so in 



Birch Ivy. 



It is a noticeable feature in most of the above cases 

 of distichous arrangement, that the bud is not exactly 

 vertical over the leaf-scar if we hold the twig erect, but is 

 displaced more or less to one side above the scar. This is 

 very conspicuous in the Lime and Elms, but is observable 

 in the others also. It is in some way connected with 



