XIV RUDIMENTS OF BOTANY. 



63. WJien each flower is sessile or placed in the axil of the bracts, 

 without a peduncle, a spike is produced : Hence the only difference 

 between a spike and raceme in, that in the former the flowers are ses- 

 sile and the latter stalked. The term spike, however, is applied in 

 those cases where the peduncle is scarcely perceptible. 



64. A spadix is a sort of spike, in which the flowers are closely 

 packed together upon a succulent axis, which is enveloped in a spathe. 



65. An ament or catkin, is a spike, the bracts or scales of which are 

 nearly of equal size and closely imbricated, and which is articulated 

 with the stem. 



66. When a bud produces flower-buds, with a little elongation of its 

 own axis, -either a head, (capitulum,) or an umbel is produced. The 

 former bears the same relation to the latter as the spike to the raceme ; 

 that is, they differ in the flower-buds of the head being sessile, and of 

 the umbel having pedicels. 



67. A raceme, the -lowest flowers of which have long pedicels and 

 the uppermost short ones, forming a sort of level top, is a corymb. 



68. A panicle is a raceme, the flower-buds of which have, in elon- 

 gating, developed other flower-buds. 



69. A panicle, the middle branches of which are longer than those 

 of the base or apex, is termed a thyrse. 



70. A panicle, the elongation of all the ramifications of which is ar- 

 rested, so that it assumes the appearance of an umbel, is called a cymt. 

 The cyme may have the lateral branches very short and the flowers 

 clustered together, forming n fascicle \ or it may be so contracted and the 

 ramification of it so little apparent, as to be confounded with the true 

 head, when it is called a gltrmcruU. 



71. In all the modes of simple inflorescence, that is those which pro- 

 ceed from the buds of a single branch, the flowers expand first at the 

 base and last at the summit. This kind of expansion is called centri- 

 petal. 



72. When the inflorescence ia compound, or the result of the expan- 

 sion of several buds or branches, the uppermost or central flowers are 

 first developed, and lastly the outer or lower ones. This kind of ex- 

 pansion is called the centrifugal. 



FLORAL IlfVELOPKS. 



73. These immediately surround the stamens and pistils and are 

 formed of one or more whorls of variously modified leaves. When 

 they consist of but one whorl, they are called calyx ; when of two 

 whorls, the outer is called calyx, the inner carol, (corolla. ) 



74. If the floral envelopes are of such a nature that it is not obvious 

 whether they consist of both calyx and corol, or calyx only, they re- 

 ceive the name of perianth, or perigonium. 



75. Some plants have no floral envelopes ; the flowers are then said 

 to be naked or achLamydeous. 



76. The calyx consists of two or more divisions, usually green, call- 

 ed sepals, which are either distinct, when a calyx 1s said to be polyse- 

 palous, or which unite by their margins in a greater or less degree, 

 when it is called monosepalous or monophyllous, ("more properly gamo- 

 sepaloui. ) 



