

XX FIRST FUINCIPLi. 



V. LEAF-BUDS. 



141. Buds arc of two kinds, Loaf-buds and Flower-buds. 



142. Leaf-buds (Bourgeon, Fr.^) consist of rudimentary leaves surrounding a 

 itaJ point, the tissue of which is capable of elongation, upwards in the form of 



stem, and downwards in the form of wood or root. 



143. Fxowee-btjdb (Bouton, Fr.) consist of rudimentary leaves surrounding a 

 point, whicrTdoes not elongate after it is once developed, and assumes, when fully 



doped, the form of reproductive apparatus. 



144. Notwithstanding this difference, a leaf-bud sometimes indicates a tendency 

 to become a flower-bud ; and flower-buds frequently assume the characters of leaf?' 

 buds ; Ex. Monstrous Pears. 



145. Leaf-buds are of two kinds, the regular and the adventitious. 



146. Regular Leaf-buds are only found in the axillae of the leaves. 



147. They exist in a developed or undeveloped state in the axilla; of all leaves, 

 and of all modifications of leaves. 



148. Therefore, they may be expected to appear at the axilla: of scales of the- 

 bud, of stipulae (183), of bractero (229), of sepals (290), of petals (291), of stamens 

 (302), and of carpclla'(354) ; in all of which situations they are generally undc->. 

 vcloped. 



149. They are frequently not called into action, even in the axillco of leaves. 



150. As regular buds are only found in the axilla; of leaves, or of their modifica- 

 tions ; and as branches are always the developement of buds, it follows that what- 

 ever may be the arrangement of the leaves, the same will be the disposition of the 

 branches ; and vice versa. 



151. This corresponding symmetry is, however, continually destroyed by the 

 developement of the buds. 



152. Leaf-buds, whicli are formed among the tissue of plants subsequently to the 

 developement of the stem and leaves, are called latent, adventitious, or abnormal. 



153. Adventitious Leaf-buds may be produced wherever there is an anastomosis 

 of woody fibre. 



154. They arc formed in the root, among the wood, and at the margin, or on the 

 surface of leaves. 



155. They are constructed anatomically, exactly as regular buds, having pith in 

 their centre, surrounded by spiral vessels, and coated over by woody fibre and cellu- 

 lar integument. 



150. llence, as adventitious buds, containing spiral vessels, can be produced 

 from parts such as the root or the wood, in which no spiral vessels previously 

 < dsted, it follows that this form of tissue is cither generated spontaneously, or is 

 produced by some other tissue, in a manner unknown to us. 



157. Leaf-buds have been sometimes confounded with roots by old botanists. A 

 bulb is a leaf-bud ; a bulbous root is a contradiction in terms. 



VI. LEAVES. 



158. A leaf is an expansion of the bark immediately below the origin of a regu-. 

 lar leaf-bud, and is an appendage of the axis (51). 



1 59. Whenever a regular leaf-bud is formed, a leaf, either perfect or rudimentary, 

 is developed also ; and vice versa. 



100. IiCaves are developed alternately, one above and opposite the other, around 

 their common axis; but in consequence of the internodia of the axis being une- 

 qually developed, leaves are often opposite or verticillate. They arc never produced 

 side by : ide. 



161. In Exogenous plants, the primordial or seed-leaves (cotyledons) arc oppo- 

 site; hence, in such plants the non-developement of the axis takes place during 

 the original formation * » t' the embryo. 



162. There is a constant tendency in opposite or verticillate leaves to become 

 alternate. 



163. This law applies equally to the arrangement of all parts that are modifica- 

 tions of leaves. 



104. A leaf consists of a petiole, a lamina, and a pai* of stipulse. 



1G5. The petiole is the channel through which the vessels of the leaf are con- 

 nected with those of I he stem ; it is formed of one or more bundles of spiral vessels 

 and woody fibre, enclosed in a cellular integument. 



