:\IORPHOLOGY OF EEPRODUCTIYK ORGANS 129 



Fia. 243. 



FiC!. 244, 



Pi:l. 243. Cone of 

 ilorsetail {Eqiiifte- 



iHiii). Fig. 244. 



Cone of Hemlock 

 Spnice (Pinus 



ranciilefui^'). 



which resembles the cones or flowers often found in the group of 

 Phanerogams laiown as Gymnosperms {fig. 244) . Similar arrange- 

 ments are found among the Lycopodinie, or Chab-inosses. In the 

 so-called flowering plants the flowers are the ultimate branches 

 or shoots of the inflorescence. They consist usually of an axis 

 bearing leaves, of which some 

 are sporophylls and bear the 

 sporangia, others are perianth 

 leaves and have only a function 

 subordinate to the former. The 

 apex of the axis itself some- 

 times constitutes the flower, as 

 in the female flower of the Yew- 

 tree, where particular branches 

 bear at their apex a terminal 

 megasporangium or ovule, "\^'hich 

 is not protected by any foliar 

 structures. In a few cases some 

 of the sporangia are borne by 

 the axis, and others by the sporo- 

 phylls, as in the Polygonaceaa, 

 the Dock family. The axis here 

 terminates in a megasporangium 

 much as in the Yew, but this is 

 covered in by a foliar outgrowth called the ovary. Lower down 

 on the axis are certain sporophylls, the stamens, which bear the 

 microsporangia, while below these again are certain perianth 

 leaves. 



The phyllotaxis of the flower, like that of the vegetative shoot, 

 may be either alternate or whorled. In the former case the 

 leaves describe a spiral round the axis ; in the latter they form 

 generally four definite whorls or series. Instances of the former 

 may be seen in the flowers of Pinus and other Conifers, and 

 among the higher plants in the Water-lily. 



Spiral phyllotaxis is most usual in the Gymnosperms, and 

 whorled in the Angiosperms. 



In one of the most highly organised of the flowers of the latter 

 group we can recognise four whorls of leaves arranged upon an 

 axis or thalamus. Usually the thalamus is terminated by the 

 ultimate whorl of leaves, but in some cases it grows out beyond 

 it, and may then bear a number of ordinary foliage leaves. 

 This is, however, regarded as altogether abnormal, and only 

 occurs in consequence of some disturbance of nutrition. The 

 VOL. I. K 



