44 



HISTORY OF THE VEGETABLE KINGDOM. 



yellow, red, brown, are owing to the different 

 degrees of oxidation of the matters contained in 

 the desiccated juices of the leaf; not unfrequently 

 the colour is influenced by numerous minute 

 fungi which spring up on the surface of the de- 

 caying leaf. How beautiful are the mellow 

 tints of an autumn forest ! more deep and gorge- 

 ous, though not so full of hope and joy, as the 

 light budding appearance of spring. A late tra- 

 veller thus remarks of the foliage of the south- 

 ern hemisphere : 



" In South America, Australia, and the Cape of 

 Good Hope, tlie trees are all evergreens. The 

 inhabitants of these and the intertropical regions 

 generally, thus lose, perhaps, one of the most 

 glorious, though to our eyes common spectacles 

 in the world, the first bursting into full foliage 

 of the leafless tree. They may however say, 

 that we pay dearly for our spectacle by having 

 the land covered with mere naked skeletons for 

 so many months. This is too true, but our senses 

 thus acquire a keen relish for the exquisite 

 green of the spring, which the eyes of those liv- 

 ing withm the tropics, sated during the long year 

 with the gorgeous productions of those glowing 

 climates can never experience." * 



The size of the leaf, as well as all the other 

 qualities, varies according to the species of plant 

 on which it grows. Nor is it always the largest 

 plant that has the largest leaf. The leaf of 

 Caltha palustris, an humble herb, is larger than 

 the leaf of the oak, though a lofty tree. The 

 largest leaf produced on any British plant is that 

 of the Tmsilago petasites, and yet it is diminu- 

 tive compared with the leaves of many plants of 

 tropical climes. The leaf of StreliUia regina 

 grows to the height of three or four feet, and is 

 eighteen inches at its greatest breadth, yet there 

 are many still larger. The leaves of the mag- 

 nificent banana have been known to grow to 

 the extent of ten feet in length, by two feet at 

 the base ; hence some fancy ^Titers have set 

 them down as tlie leaves which our first parents 

 employed to clothe their nakedness. The leaves 

 of some of the palms are from ten to fifteen feet 

 in length, and even the smallest leaflets are three 

 feet. A tree in full foliage affords a most grate- 

 ful shade both to man and animals, especially 

 under tropical suns, where indeed the foliage is 

 largest and most luxuriant ; even in temperate 

 regions, the cool canopy of a wide spreading 

 tree, and the pleasing and refreshing green of 

 its foliage, are grateful luxuries during the heats 

 of summer. Hence the fame of the celebrated 

 groves of Arcadia, where Plato and his succes- 

 sors delivered their lectures in philosophy; and 

 the cool and shady, though less classical avenues, 

 of lime and chestnut trees of our own country. 



* Darwin's Natural History of a Voyage to South 

 America. 



The odour of some leaves is extremely grateful, 

 particularly when bruised with the hand, as the 

 myrtle, balm, thyme, and many others. Some 

 leaves retain this aromatic flavour for several 

 years, even in a dried state, as is the case of 

 verbena and lavender. The leaves of many of 

 the geranium tribe are extremely sweet scented, 

 and the odour of many others are well Jcnown. 



The leaves of cei-tain vegetables are extensively 

 used as articles of food, such as cabbage, lettuce, 

 celery, parsley; and cultivation has greatly altered 

 and inhanced them as dietetic substances. The 

 grasses, and every species of green herbage, also 

 form the food of a large proportion of animals. 

 There is scarcely a leaf of almost any species of 

 plant but what is not appropriated as the food of 

 certain insects. Leaves are also used as medi- 

 cines; such are tlie leaves of foxglove, senna, 

 and others. 



CHAP. X. 



THE STIPULES. 



The Stipules are organs connected with the 

 leaves, existing only in the dicotyledonous plants, 

 though not always present. They are small 

 scale-like or leafy appendages, at the point where 

 the leaves come off from the stem, and are com- 

 monly in paire, there being one on each side of 

 the petiole, as in the hornbeam and lime. They 

 are more frequently free, not being attached to 

 the petiole ; but, at other times, tliey are united 

 to the base of that organ, as in the genus Rosa. 



The Stipules afford excellent cliaj-actei-s for 

 the arrangements of plants. When a vegetable 

 of a natural family has these organs, it is very 

 seldom the case that all the others are not equally 

 provided with them. Thus they exist in all 

 plants of the families of Leguminosce, Rosaceoe. 

 Tiliaceos, &c. As they fall off very easily when 

 they are free, their absence might sometimes 

 induce one to suppose a plant destitute of them ; 

 but this error may easily be avoided by observ- 

 ing that they always leave on the stem, at the 

 place where they were attached, a small cicatrix, 

 or scar, which attests the fjict of their having 

 existed. 



In the coffee, cinchona, and other similar 

 plants, the stipules are situated between the 

 leaves, and appear to be nothing more than 

 abortive leaves. In fact, in the same family of 

 our climates, such as the galiums, they are sub- 

 stituted by true leaves, which then form a whorl 

 around the stem. Some plants, as the barberrj', 

 have single stipules. Where there are two, they 

 are always distinct from each other; but some- 

 times they unite and are connate, as in the hop. 

 The stipules may be united within the axil of 



