Xll RUDIMENTS OF BOTANY. 



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, or an umbel is produced. The former bears the same re- 

 lation 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 up- 

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



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

 developed other flower-buds. 



G9. 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 arrested, 

 so that it assumes the appearance of an umbel, is called a cyme. The cyme 

 may have the lateral branches very short and the flowers clustered together, 

 forming a 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 

 glomerule, 



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

 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 centripetal. 



72. When the inflorescence is compound, or the result of the expansion 

 of several buds or branches, the uppermost or central flowers are first de- 

 veloped, and lastly the outer or lower ones. This kind of expansion is called 

 the centrifugal. 



FLORAL ENVELOPES. 



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 usually called calyx; when of two whorls, the outer 

 is called calyx, the inner corolla. 



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

 whether they consist of both calyx and corolla, or calyx only, they receive 

 the name of perianth or perigonium. 



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

 naked or achla 



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

 sepals, which are either distinct, when a calyx is said to be polysepalous, or 

 which unite by their margins in a greater or less degree, when it is called 

 monosepalous or monopJiyllous, (gamosepalous.} 



77. The corolla consists of two or more divisions, more or less colored, 

 called petals ; when the petals are distinct, a corolla is said to be polypeta- 

 lous ; when they are united by the margins, it is called monopetalous, (gamo- 

 petalous.} 



78. When all the petals are equal, the corolla is said to be regular, but 

 when they are unequal in size or cohere unequally, it is then called irreg- 

 ular. 



79. The regular monopetalous corolla varies greatly in its form, being 

 campanulate or bell-shaped, infundibuliform or funnel-shaped, rotate or wheel- 

 shaped, &c. 



