GENERAL CHARACTERS OF PLANTS 



11 



sometimes so large tliat it almost completely encloses the flower, 

 or even a cluster of flowers. 



The flower is the reproductive part of the plant, being concerned 

 in the ])roduction of the seeds ; but the organs directly connected 



INPEIUOR (1) AND SUPERIOR (2) OVARY. 



with the seed-formation are the pistil and the stamens, the former 

 containing the ovules, and the latter producing the pollen cells 

 by means of which the ovules are impregnated. Thus the stamens 

 and the pistil are the essential parts of the flower, though the corolla 

 and the calyx may perform some subsidiary function in connexion 

 with the reproduction of the species. 



This being the case, a flower may be described as perfect if it 

 consists of stamens and pistil only, without any surrounding calyx 

 or corolla ; and imperfect if it possesses no pistil or no stamens, 

 regardless of the presence or absence of calyx and corolla. 



The two outer whorls of a well-developed perfect flower (calyx 

 and corolla) together form the perianth. Some flowers, however 

 have only one whorl outside the 

 anthers, representing both the calyx 

 and corolla of the more highly or- 

 ganised flower. This one whorl, 

 therefore, is the perianth, and its 

 parts are not correctly termed either 

 petals or sepals, since they represent 

 both. 



A perfect flower is sometimes 

 spoken of as bisexual, for it includes 

 the two sexual organs of the plant — 



the ovary or female part, producing the ovules ; and the stamens 

 or male part, which is concerned in the impregnation or fertilisation 

 of the ovules. 



Many plants produce only unisexual (and therefore imperfect) 



UNISEXUAL FLOWERS OP THE 



NETTLE 



1. Pistillate. 2. Staminate. 



