30 THE VEGETATIVE SHOOT 



the stem which bears them, the older ones being further removed 

 from it in regular order — that is, they arise in acropetal suc- 

 cession, and adventitious leaves are never met with. 



Ex. 20. — I. Sow beans in pots or boxes containing a mixture of damp sand 

 and garden soil. 



Cut longitudinal sections, and examine the structure of the stem and terminal 

 bud of a seedling as soon as it has come above the surface of the soil. 



2. Watch the development of the stem up to the time of unfolding of 

 the green leaves. 



Observe the rudimentary character of the first leaves. 



3. Make small marks on the stem about a quarter of an inch apart with 

 Indian ink, and observe which part elongates most. 



4. Make similar observations upon the seedlings of mustard and peas. 



3. While numerous annuals, such as mustard and charlock, and 

 some perennials, resemble the bean, many plants differ somewhat 

 from it in the development of the plumule. Instead of the latter 

 growing at once into a long shoot, bearing leaves at some dis- 

 tance from each other, the primary axis within the plumule 

 elongates very little, its internodes remain very short, and the 

 leaves arising upon it appear crowded together, usually in the 

 form of a rosette, a short distance above where the cotyledons 

 were placed ; this form of stem with short contracted inter- 

 nodes is well illustrated in the first season's growth of mangels, 

 turnips, carrots, certain thistles, and red clover. In such plants 

 as these, the primary root and hypocotyl become much thickened 

 by the deposition within them of reserve-food prepared by the 

 leaves, and it is only during the following year that the 

 growing-point of the stem, which is hidden in the centre of the 

 rosette, elongates and produces a shoot with long internodes, 

 and bearing a series of new leaves at considerable intervals. 



In the onion and many bulbous plants the primary stem also 

 remains very short, and the reserve-food prepared by them 

 are deposited in the bases of the leaves, instead of being 

 stored in the root and stem, as in the former instances (see 

 Fig. 24). 



