RUDIMENTS OP BOTANY. Xlll 



48. Leaves are originally continuous with the stem, bat afterwards, 

 from a cause which is still unknown, an articulation more or less com- 

 plete takes place and the fall of the leaf ensues. 



49. The mode in which leaves are arranged within their bud is call- 

 ed vernation or gemmation. This varies much in different groups of 

 plants. 



FLOWER-BUDS. 



50. The flower-bud consists of imbricated rudimentary or metamor- 

 phosed leaves, the external or inferior of which are usually alternate, 

 and the internal or superior always verticillate or opposite ; the latter 

 are called floral envelopes and reproductive organs. 



51. The leaves from the axils of which the flower-buds arise are call- 

 ed bracts, (bractea,} or floral leaves ; and those leaves which appear on 

 the pedicel between the bracts and calyx, are called bracteolce. These , 

 although essentially distinct, are often confounded with the former. 



52. When a single bract is rolled together, highly developed, and 

 coloured, and is placed at the base of the form of inflorescence called a 

 spadix, it is named a spathe, (spatha. ) 



53. When several bracts are verticillate or densely imbricated around 

 the base of the forms of inflorescence called the umbel, or capitulum, 

 they are termed an involucre ; and those at the base of each partial 

 umbel are called involucels. 



54. Small imbricated bracts are often called scales ; as in the Com- 

 posite. 



55. Bracts, when placed immediately below the stamens and pistils, 

 as in apetalous flowers, are only distinguished from the calyx by being 

 alternate with each other, and not verticillate ; hence the glumes and 

 paL&E of grasses are bracts and not calyx. 



56. The elongation of the axis of the flower bud from the point of 

 its connexion with the stem, as far as the floral envelopes, is called the 

 peduncle. 



57. When several peduncles spring from the axis near to each other, 

 the axis is termed a rachis, and the peduncles themselves are called 



58. Those axes that spring from the earth and bear no true leaves 

 are denominated scapes. 



59. The modes in which the flower-buds are arranged are called 

 forms of inflorescence ; and the order in which they unfold, is called the 

 order of expansion. 



INFLORESCENCE, 



60. When a flower-bud gives rise to only one flower, terminal on its 

 peduncle, and the axis of the plant does not elongate beyond the bud, 

 the flower is commonly called terminal and solitary. 



61. When the axis, however, continues to elongate and the bract re- 

 tains the form and size of a leaf, the flower is called axillary and soli- 

 tary. 



62. If the buds instead of giving rise to one terminal flower have the 

 axis elongated, bearing several flowers, and each flower on a peduncle, 

 a raceme is formed. 



la* 



