STEMS, LEAVES, AND BUDS 



35 



separated from each other. Marks 

 made upon the stem as previously 

 explained for the root in Ex. 15, 

 reveal the fact that the increase in 

 length takes place at the tip of 

 the shoot. After reaching a certain 

 length the lowest intervals between 

 the leaves cease to elongate; the 

 upper, younger and shorter ones 

 also lengthen and cease 

 in a similar manner, to 

 be followed in turn by 

 still younger parts of the 

 stem nearer the tip. The 

 stem, before the growing 

 season is over, may thus 

 reach a height of two or 

 three feet, or even more, 

 the extreme tip, or grow- 

 ing-point as it is called, 

 remaining young all the 

 time, and acting as a 

 manufactory for the ad- 

 dition of more stem and 

 leaves. The growing- 

 point, which is of a 

 tender and delicate 

 nature, is protected by 

 the enfolding young 

 leaves, the latter aris- 

 ing as outgrowths from 

 its external surface. The 

 youngest leaves are al- 

 ways nearest the tip of 



Epicotyl of bean, with plumule. 



Longitudinal section of the same ; ep epicotyl ; 

 p terminal growing point of ihe plumule ; a a 

 leaf in whose axil is a bud b' ; b buds in axils of 

 inner leaves of the plumule. 



Epicotyl, with plumule unfolding. 



Later stage of growth of 3, showing connection 

 with bean seed ; ep epicotyl ; a first leaf 

 (rudimentary), in whose axil is bud U ,*ysecond 

 leaf (rudimentary) ; c and e ordinary foliage 

 leaves ; g buds in axils of the cotyledons ready 

 to develop into stems which may come above 

 ground. 



