92 Anatomy and Physiology. 



grow very near the blossom, and are often mistaken for the 

 flower; they are frequently painted as in the hydrangea, whose 

 pink and lilac bractea are often taken for real flowers, a mistake 

 which is, in our opinion, of very little importance, as the only mode 

 of telling the difference, when it can be told, is that they possess 

 few of the regular organs of the flower, and produce neither fruit 

 nor seed. In the lime tree, painted cup, sage, &c., they can be 

 easily examined. 



Leaves vary exceedingly in point of size ; from the extreme 

 minuteness of those of the moss, which sometimes require a 

 microscope to obtain a fair view, to the talipot of Ceylon, which 

 are fifteen feet broad and twenty long, a single one being suf- 

 ficient to shelter twenty men. The natives, when ^ travelling, 

 make huts of them, use them as paper, and finally adore them. 



Climate seems to have a great deal of influence in regard to 

 the fall of leaves. Under the equator the trees are perpetually 

 verdant, and the leaves rarely fade till they are six years old ; yet 

 moved to a colder latitude they will be annually naked. The 

 opposite holds true with Northern plants transported to Southern 

 regions. The currant, originally a native of the colder parts of 

 Europe, became perennial when taken to St. Helena; and re- 

 versing the example, the evergreen quince of the South parts 

 every year with its leaves in our latitude. If the kidney bean is 

 protected from the frost it will continue green all the year round. 

 We would not be understood to say that an evergreen leaf lasts 

 as long as the plant All such, on the contrary, as well as the an- 

 nual and perennial, throw them off; the only difference being, 

 that we do not notice their loss, if others come out in their stead, 

 and the same appearance is still presented to us. All kinds of 

 plants are short-lived, no separate part lives a great while ; new 

 leaves, new bark, new wood must be continually formed, or the 

 whole will decay. We will speak of this hereafter, but will merely 

 state at present that when the vital principle of the leaf has done its 

 work, when the main-spring is unwound as it were, the separate 

 part, like a crushed finger, dies, and the living part casts it off. 



One would naturally expect that large trees would put forth 

 large leaves, as they are well able to endure the burden ; but it 

 is found that no such proportion exists, except perhaps in the case 

 of the talipot, which exceeds in size and dimensions a ship's mast. 

 The leaves of the oak will not compare with those of the burdock, 



