136 BOTANY AND PHARMACOGNOSY. 



developing under the leaves and sometimes underground. Of the 

 plants producing cleistogamous flowers, the following may be 

 mentioned : various species of Viola, Polygala, etc. 



Classes of Flowers. — As we have seen the megasporo- 

 phylls and microsporophylls in the Gymnosperms are borne on 

 separate branches, thus giving rise to two kinds of flowers, or 

 cones. While the separation of the stamens and pistils is exempli- 

 fied in a number of plants in the Angiosperms, still it is not the 

 rule and these two elements are usually borne close together on the 

 same axis, i.e., they both enter into a single flower structure. Such 

 a flower is said to be hermaphrodite or bisexual, and most of the 

 conspicuous flowers are of this kind, as roses, buttercups, lilies, 

 etc. Inasmuch as the stamens and pistils constitute the essential 

 elements of the flower, hermaphrodite flowers are also spoken of as 

 PERFECT providing the stamens and pistils are capable of exer- 

 cising their generative functions. When the stamens and pistils 

 occur in separate flowers the flowers are said to be unisexual or 

 IMPERFECT, as in willow, oak, hickory, etc. A flower having only 

 a pistil or pistils is called pistillate ( Fig. 79, A), while one hav- 

 ing only a stamen or stamens is staminate (Fig. 135). The 

 staminate and pistillate flowers may be borne on the same plant, 

 when it is said to be moncecious, as in castor bean, chestnut 

 (Fig. 72), alder; or they may be borne on separate plants, when 

 the plant is called dicecious, as in willows and poplars. Plants 

 bearing hermaphrodite and unisexual flowers on the same indi- 

 vidual plant or on different individuals are called polygamous, 

 as in Ailanthus. 



A complete flower is one which possesses both kinds of essen- 

 tial elements and both kinds of floral envelopes, and is symmet- 

 rical when the parts are alike and when the number of parts in 

 each circle is the same or when the number in one circle is a 

 multiple of that in the others ; as a rule the number of stamens is 

 some multiple of one of the other parts, as in geranium (Fig. 155), 

 where we find five sepals, five petals, ten stamens and five pistils. 



Flowers are also spoken of as regular or irregular, accord- 

 ing to whether all the parts of a cifcle are uniform in shape or 

 not-; th^ flowers of geranium are riegular while those of violets 

 are irregular. Regularr floAversi are. also spoken of as acting- 



