178 GENERAL BOTANY 



broadening of the rachis increases the area of green 

 tissue which can do the work of assimilation, and 

 being thick and tough this part would not suffer so 

 much in a drought as would thin leaflets. The 

 spines of course prevent animals eating the leaves 

 and small branches, for some animals are very fond 

 of aniseed oil, and here again as before the protection 

 is all the better because of the shortness amounting 

 almost to total absence of the axillary branch, so that 

 the leaves are massed together close to the spines. 



CITRUS MEDICA, L. 



The Orange tree. 



The branches are green and angular, the leaves 

 are spirally placed, i.e. are alternate, and at the base 

 of each is a thorn, placed somewhat to one side of 

 the minute axillary bud. On the upper branches of 

 older trees these thorns are sometimes replaced by 

 leaves, from which we must conclude that the thorn 

 is not a modified branch, as it looks at first sight, 

 but represents the first leaf of the axillary branch, 

 which does not ordinarily develop further than the 

 bud stage. This too in FERONIA. 



The leaf itself consists of two parts, a broad winged 

 stalk and a blade, and at the junction of these two 

 there is a sort of joint, a thing we never find in ordinary 

 simple leaves. 



Compare this now with the leaf of FERONIA, which 

 has several leaflets attached to the winged rachis, by 

 joints very much like this in appearance. If there 

 were on FERONIA only one leaflet, it would be exactly 

 like the leaf of the Orange. We conclude, therefore,. 



