CHAPTER IV. 



THE VEGETATIVE SHOOT : STEMS, LEAVES, 

 AND BUDS. 



I. It has been already noticed that the seedling bean plant consists 

 of a descending portion, the root, and an ascending part which 

 comes above ground. The latter is known as Xhe. primary shoot, 

 and consists of an axis — the stem — upon which are arranged a 

 series of lateral appendages which are called leaves. The points 

 on the stem to which the leaves are attached are usually slightly 

 thickened, and are called nodes or 'joints,' the lengths of stem 

 between them being termed internodes. Flowers ultimately 

 .arise upon the shoot, and it is one of the characteristics of seed- 

 bearing plants that seeds are always produced on their shoots and 

 never on roots. For the present, however, flowers may be left for 

 future consideration, and attention paid to the origin and nature 

 of the vegetative shoot or stem with its ordinary green leaves. 



2. In the earliest stages of the development of a bean plant the 

 primary shoot is very short and bears the cotyledons or primary 

 leaves, its tip ending in the plumule. 



The latter is a bud, and at the time when the seed commences 

 to germinate, its parts cannot be fully made out by observations 

 with the naked eye. As soon as it comes above ground, however, 

 the bud is found, on examination, to consist of a short stem 

 hidden by a number of enfolding leaves. An external view of it 

 in this stage is given at i, and a longitudinal section at 2, Fig. 1 1. 



As growth proceeds, the short stem inside the bud elongates, 

 and the leaves, which at first are crowded upon it, become 

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