FLOWER-GARDENING. 143 



bractese of the involucrum form other Daisy-heads in their 

 axillae; or, as in certain Roses, in which the capillary leaves 

 develop leaf-buds in their axilla, so that the flower becomes a 

 branch the lower leaves of which are colored and transformed, 

 and the upper green, and in their ordinary state. 



184. Discoid compound flowers are those in which the cen- 

 tral florets of a* flower-head acquire corollas, like those of the 

 circumference, as in the Dahlia ; the cultivated variety of which 

 should be called discoid, and not double. 



185. Thesfe two last are so essentially different from double 

 flowers, that whatever laws may be supposed to govern the 

 production or amelioration of double flowers, can have no 

 "elation to proliferous or discoid compound flowers. 



VII. SEXES. 



186. The sexes consist of two or more whorls of transformed 

 leaves, of which the outer are called Stamens (188), and the 

 inner Pistillum (191). 



187. They are known to be modifications of leaves, because 

 they very frequently are transformed into petals, which are 

 demonstrably such (149), and because they occasionally revert 

 to the state of leaves. 



188. The stamens bear at their apex an organ, called the 

 anther, which contains a powder called pollen. 



189. When the anther is full grown it opens and emits the 

 pollen, either dispersing it in the air in consequence of the 

 elasticity with which it opens ; or depositing it upon the stig- 

 mata (191); or exposing it to the action of wind, or such 

 other disturbing causes as may liberate it from its case. 



190. The pollen consists of exceedingly minute hollow bulls, 

 or cases, containing myriads of moving particles, which are the 

 fertilizing principle of the stamens. 



191. The pistillum has at its base one or more cavities or 

 cells, in which bodies called ovula are placed ; and at its apex 

 one or more secreting surfaces, called stigmata. 



