Reviews. — Lindlcifs Theory of Horticulture. 23 



oxywen instead, gets into a morbid condition, and dies: it is then 

 tlirovvn off. This phenomenon, which we call the/a7/ of the leaf, is 

 going on the whole year round, except mid-winter, in some plant or 

 other. Those which lose the whole of their leaves at the ai)proach 

 of winter, and are called deciduous, begin, in fact, to cast their leaves 

 within a few weeks after the commencement of their vernal growth; 

 but the mass of their foliage is not rejected till late in the season. 

 Those, on the other hand, which are named evergreens, part with 

 their leaves much more slowly: retain them in health at the time 

 when the leaves of other plants are perishing; and do not cast them 

 till a new spring has commenced, when other trees are leafing, or 

 even later. In the latter class, the functions of the leaves are going 

 on during all the winter, although languidly; they are constantly at- 

 tracting sap from the earth through the spongelets, and are, there- 

 fore, in a state of slow but continual winter growth. It usually hap- 

 pens that the perspiratory organs of these plants are less active than 

 in deciduous species. 



In general, a leaf is an organ of digestion and respiration, and 

 nothing more: some leaves have, however, the power of forming 

 leaf-buds, if placed in or upon earth, under suitable circumstances. 

 The Bryo|)hyllum calycinum forms buds at the indentations of its 

 margin; Malaxis paludosa throws off young buds from its margin; 

 Tellima grandiflora occasionally buds at the margins of its leaves: 

 the same thing happens to many ferns; and several other cases are 

 known. 



The florist and pomologist observe many singular trans- 

 mutations in double flowers, and in monstrous fruits, which 

 are thus explained: — 



Notwithstanding the difference in form and office of the parts of 

 a flower, they have evidently a strong tendency, in cultivated plants, 

 to change into or assume the appearance of each other. In the 

 Po{)py, the Garden Anemone, and many others, the stamens change 

 into petals; in the Anemone, the Raimnculns, &c., the pistil changes 

 into petals; in the Primrose, Cowslip, &c., the calyx changes into 

 petals; in the Houseleek, the stamens become pistils; and so on. 

 Hence the origin of double flowers. In a double Barl)adoes Lily, 

 described by me in the Transaclions of the Horticultural Society, in 

 which the parts were very much confused, the young seeds were 

 borne by the edges of the stamen-like petals. 



In their ordinary state the parts of a flower are extremely unlike 

 leaves, and each has its allotted office, which is not the office of a 

 leaf; they are also incapable of forming leaf-buds in their axils. 

 But, although such is the case, there is found a strong and general 

 tendency on the parts of both the floral envelopes and sexes to 

 change to leaves, like the leaves of the stem. In the white clover 

 (Trifolium repens,) all the parts often become leaves; in the Frax- 

 inella, this has also been remarked; so has it in the Nasturtium, in 

 Sieversia montana, and many other instances. A partial alteration 

 into leaves is of very frecjuent occurrence in the parts of a flower. 

 In the Rose, the sepals and pistil are frequently changed into leaves; 

 in the Double Cherry, the pistil is almost always to be found in the 



