90 AI-TERATION OF KJSITION. 



the extremity of the axis, a position which, under 

 ordinary circumstances, no leaf could assume. The 

 explanation given by the Belgian professor is, that the 

 axis in this case, instead of throwing off a pair of leaves, 

 one on each side, had from some cause or another 

 produced only one; this one not only being much 

 larger than ordinary, but brightly coloured, thus 

 assuming some of the characteristics as well as the 

 position of the inflorescence. 



Alterations in the usual arrangement of leaves, how- 

 ever, are not always dependent on or coexistent with 

 other teratological changes, but may simply depend on 

 a natural elongation of the internodes, or on fission or 

 multiplication ; for instance, in some conifers, such as 

 the Larch, {Abies Larix) or Pinus 2>inea, there may be 

 found at different stages in the growth of the branches 

 leaves in crowded fascicles or tufts ; while, when 

 growth is more rapid, the leaves may be disposed in 

 a spiral or alternate manner. 



In the yew (Taxus) the leaves at the ends of the 

 shoots not unfrequently lose their usual distichous 

 arrangement and become arranged in a close spiral 



Fio. 42. Altered arraDgement of leaves of yew, Taxus haeeata. 



manner, the elongation of the shoot being arrested. 

 This appears to be the result of the injury effected by 

 some insect. 



