428 



BOTANY 



regarded phylogenetically as metamorphosed foliage-leaves, although 

 in most cases they in no wise resemble them, and, like the sporophylls 

 of the Eqidsetaceae and most of the Lycopodiaceae, they serve merely to 

 produce and bear the spores. Staminal and carpellary leaves 



SPRING FROM THE SUMMIT OF AN AXIS, THE FURTHER GROWTH OF 

 WHICH, EXCEPT IN THE FEMALE FLOWERS OF CYCAS, IS TERMINATED 



BY their production ; they are closely aggregated, usually in whorls, 

 but less frequently they assume a spiral arrangement. 



In the majority. of cases the reproductive axis gives rise im- 

 mediately below the stamens and carpels to other special leaves, which, 



although themselves sterile, 

 are functionally connected 

 with the sporophylls, and 

 similarly exhibit an essential 

 dissimilarity to foliage-leaves. 

 Like the sporophylls, which 

 at times become modified into 

 similar sterile leaves, these 

 leaves almost always spring 

 from the axis in whorls, and in 

 other respects they show a 

 closer relation to the sporo- 

 phylls than to the foliage - 

 leaves. Collectively they form 

 the perianth (Fig. 357, k, c). 

 The shoot or part of a 

 shoot comprising the peri- 

 anth, the sporophylls, and the portion of the axis from which 

 THEY spring, IS TERMED A flower. If the perianth is lacking, the 

 flower is naked. The stamens of a flower are designated collectively the 

 ANDRCECIUM, the carpels constitute the GYN03CIUM. When both andrce- 

 cium and gyncecium are represented in the same flower, the flower is 

 hermaphrodite ; in that case the gyncecium occupies the centre 

 of the flower. When either the androecium alone or the gyncecium 

 alone is present, the flower is unisexual or DICLINOUS. If diclinous 

 flowers of both sexes occur on the same plant, it is said to be 

 monoecious. If, however, a plant produces flowers of one sex only it 

 is termed dkecious ; on the other hand, if it develops at the same 

 time both unisexual and hermaphrodite flowers, it is termed POLY- 

 GAMOUS. 



From the constant occurrence of flowers, it is often customary to 

 refer to the Phanerogams as the Flowering Plants. It must not, 

 however, be concluded that this is characteristic of the Phanerogams 

 alone, for the aggregated sporophylls of the cones of the Equisetaceae or 

 of the spikes of the Lycopodiaceae also exhibit all the essential charac- 

 teristics of flowers, although in a less advanced degree of development 



Fro. 357. — Flower of Paeonia peregrina, in longitudinal 

 sectien. 7j and c, Perianth a, androecium g, gyn- 

 cecium. (Nat. size.) 



