SECT. I 



MORPHOLOGY 



23 



in our latitudes, the buds of shrubs and trees are usually invested, 



in winter, with scale -like leaves or BUD -SCALES (Fig. 21). These 



are rendered still more effective as protective 



structures by hairy outgrowths and excretions 



of resin and gum, and also by the occurrence of 



spaces filled with air between the scales. Not 



infrequently the subtending leaf takes part in 



the protection of its axillary bud, the base of 



the leaf- stalk, after the leaf itself has fallen, 



remaining on the shoot as a cap-like covering 



for the winter bud. The buds of tropical plants, 



which have to withstand a dry period, are 



similarly protected ; but where the rainfall is 



evenly distributed throughout the year buds 



develop no such means of protection. 



In many deciduous trees, such as the Willow, the 



terminal buds of the year's growth regularly die. In 



nearly all trees many buds, usually the fiist- formed 



buds of each year's shoot, seem able to remain dormant 



during many years without losing their vitality : these 



are termed dormant buds. In the case of the Oak or 



, 1 n 1 1 1 /. Fi(!. 21.— Winter buds of the 



Beech such latent buds can endure for hundreds of years ; ^^^^^^ ^^^^^^^^ silvatka). kns, 



in the meantime, by the Bud-scales. (Nat. size.) 

 elongation of their con- 

 nection with the stem, they continue on its surface. 

 Often it is these, rather than adventitious buds, 

 which give rise to the new growths formed on older 

 parts of stems. It may sometimes happen that 

 the latent buds lose their connection with the 

 woody parts of their parent stem, but nevertheless 

 grow in thickness, and develop their own wood ; 

 they then form remarkable spherical growths within 

 the bark, which may attain the size of a hen's egg 

 and can be easily separated from the surrounding 

 bark. Such globular shoots are frequently found 

 in Beech and Olive trees. 



The Metamorphosis of the Bud. — The 



BULBILS and GEMMAE, which become separ- 

 ated from the parent plant and serve as a 

 means of reproduction, are special forms of 

 modified buds. To facilitate the storage 

 of reserve nutritive substances they have 

 usually the form of small tuberous bodies. 

 Many plants owe their specific name to 

 the fact that they produce such bulbils, 



as, for example, Lilkim bulbiferiim and Dentaria bulhifera (Fig. 22). 



Bulbils are also produced in the inflorescences of Allium and Gagea. 



i 



Fig. 22. — Shoot oC Dentariahulbifera 

 bearing bulbils, hr. (Nat. size.) 



