DEVELOPMENT OF LEAVES AND STIPULES 47 



ment being completed by growth in a zone of cells 

 situated just above its base (intercalary growth). So 

 that, as Schleiden has pointed out, while the apex is 

 the youngest part of the shoot, it is the older part 

 of the leaf. The projection gradually widens, and 

 often occupies more than half the circumference, thus 

 affording a possible explanation of the fact that, while 

 the cotyledons are opposite, the leaves are in so many 

 cases alternate. 



The rudimentary leaf consists of undifferentiated 

 cellular tissue, and does not at first contain any vessels. 



It is no part of my present intention to deal with 

 this interesting subject in detail, but I will give a few 

 cases in illustration, taking that of ordinary foliage 

 leaves, for in those which are intended as bud-pro- 

 tectors the stages are very different. 



AUCUBA 



On account of its simplicity, I will commence with 

 the common Aucuba japonica of our shrubberies. The 

 leaves of Aucuba are opposite, ovate, and without stip- 

 ules. They commence as two slight projections, each of 

 which broadens at the base, and finally occupies one- 

 half of the circumference of the stem (figs. 59, 60), so 

 that they are concave on the inner side and almost 

 cover over the growing-point. They gradually elongate 

 (fig. 61), and from being at first slightly curved 



