Vegetable Physiology, 396 



pines, is a strobilus or cone. Ex : Zamia, a species of which 

 is called Coontie in Florida, and from the thickened stems of 

 which is made a kind of Arrow root. From the trunk of Cy- 

 cas, is obtained a kind of Sago. 



VEGETABLE PHYSIOLOGY. 



NUMBER NINE. 



DEVELOPEMENT OF LEAVES. 



When leaves are first produced, they are small, delicate in 

 texture, pale in color, and packed closely together, forming 

 what is called a leaf-bud. Some of the outer ones are gene- 

 rally more firm in texture and darker in color, and fold over 

 each other so as to protect the more tender ones within. These 

 are often quite different from the other leaves in aspect, and 

 are usually called scales ; but the distinction is not real, since 

 on opening the bud, it will be seen that they pass gradually 

 into true leaves. The young leaves are beautifully folded 

 together, in such a manner as to occupy the least possible 

 space, and the mode in which this is done differs in different 

 families of plants. Any one may examine this, with the cer- 

 tainty of being greatly interested, by cutting through the leaf- 

 buds with a sharp knife, when they are swelling, but before 

 they begin to expand.* The outer scales are sometimes 

 covered with a thick down, as a protection against cold, and 

 sometimes, as in the Horse-chestnut, they are coated with a 

 gummy substance. In most buds, the young leaves may be 

 easily observed to be arranged around a common centre or 



* An excellent subject for this purpose is the leaf-bud of the Tulip-Tree. 

 The buds are large, and the vernation very curious, being of the kind termed 

 oppressed. 



