122 BOTANY AND PHARMACOGNOSY. 



perpetuation of species, other methods of reproduction are fol- 

 lowed in nature, the most important one of which depends upon 

 the development of flowers and the production of seed. 



While the flower is a very complicated structure in many 

 cases, the definition given it by some writers is very simple. It 

 is defined as a branch which bears sporophylls. As we have 

 seen, a sporophyll is a leaf which bears sporangia. According to 

 the definition given, the strobiles or cones of the Gymnosperms 

 and certain Pteridophytes, as the horsetails and club mosses, 

 are entitled to rank as flowers. In Angiosperms other leaves may 

 be present, and these are known as the floral leaves. The 

 flower then in Angiosperms is made up of sporophylls which are 

 essential, and floral leaves which may or may not be present. But 

 in speaking of the sporophylls of the flower in Angiosperms it is 

 customary to vise terms which were applied to them before their 

 relation to the similar organs in the Gmynosperms and Pterido- 

 phytes was understood. Thus the microsporophylls as already 

 pointed out, are known as stamens, and the megasporophylls as 



CARPELS. 



For a great many years botanists taught that the stamens and 

 carpels are transformed foliage leaves, — in other words that they 

 are derived from foliage leaves, but in more recent years the view 

 has been established that they arise as independent members, are in 

 fact as independent as the foliage leaves themselves. Various 

 transformations or modifications may and do occur, but these 

 are not confined to the foliage leaves alone for under certain con- 

 ditions the sporophylls may assume the character of floral leaves. 



It is true that in the case of some ferns, the sporophylls bear 

 a strong resemblance to foliage leaves, as in Aspidium Felix mas 

 (Fig. 277), but this does not necessarily prove that the sporo- 

 phylls of Angiosperms are transformed leaves, but only that the 

 further back we go, the less the degree of differentiation of parts 

 until we reach the unicellular algae. 



The several parts of the flower are arranged more or less 

 compactly at the terminus of an axis known as the flower branch, 

 the special portion bearing these parts being known as the torus 

 (sometimes spoken of as the receptacle), and that portion below 

 the flower proper as the flower stalk (Fig. 83, PE). The carpel 



