628 



PART ITI. THE CLASSIFICATION OF PLANTS. 



pericarp : seed without endosperm. Herbs with scattered leaves, 

 mostly climbers, with tendrils growing by the side of the leaves. 



There is considerable difference of opinion as to the morphological nature of 

 the tendril in this order, but it appears to be essentially a leaf, in fact the first 

 leaf of the flowering-shoot which arises in the axil of the related foliage-leaf : 

 the vegetative branch, which is always developed by the side of the flowering- 

 shoot, seems to spring from the axil of the tendril. The tendril often bears a 

 number of branches at its distal end, but, whether simple or branched, its 

 structure shows that the proximal portion corresponds in structure to a petiole, 

 whilst the distal irritable portion (including the branches) has a bilateral 

 structure which suggests correspondence with a lamina. 



Cucurbita Pepo is the Pumpkin : the genus Cucumis has free stamens ; 

 Cucumis t>ativa is the Cucumber, and Cucumis Melo is the Melon : Citrullns 



vulgaris is the Water Melon. 

 The genus Bryonia has a small 

 white corolla ; the loculi of the 

 ovary are 2-seeded, and the 

 fruit is a succulent berry ; B. 

 dioica is common in shrubberies 



Order 5. CACTACE^B. 

 Flowers acyclic, epigyn- 

 ous, with numerous sepals, 

 petals, and stamens, which 

 gradually pass into each 

 other : ovary unilocular, 

 with three or more parietal 

 placentae : ovules horizon- 

 tal ; endosperm little or 

 none : stems of the most 

 various forms : leaves usu- 

 ally represented by tufts 

 of spines. They are in- 

 digenous to the dry dis- 

 tricts of tropical and sub- 

 tropical America, but 

 many have been intro- 

 duced into the eastern hemisphere : however, a species of the genus 

 Rhipsalis (B. Cassytha) is indigenous to South Africa and Ceylon. 



The Cactaceae are typically xerophilous plants : in consequence of the great 

 reduction of the foliage-leaves, their transpiration is comparatively slight, and 

 the succulent stems serve to store relatively large quantities of water. They 

 are protected from being eaten, by the development of numerous spines. 



FIG. 428. A Longitudinal section of ? flower of 

 Cucumis: / ovary; sk ovules; fc calyx; C corolla; 

 n stigma ; st' rudimentary stamens. B Longitudi- 

 nal section of <J flower; st stamens ; 71' rudimentary 

 ovary; the corolla (c) is not all shown (somewhat 

 mag.). Floral diagram of Cucurbita. 



