584 PART 111. — THE CLASSIFICATION OF PLANTS. 



their lower part of ? flowers and at their upper of ^ flowers, whilst others 

 have only ^ flowers. In the axil of each bract there are usually either seven 

 <? or three ? flowers : the latter are invested by the bracteoles a and j3, and 

 by a cupule formed by the other four bracteoles ; the cupule, which is covered 

 with prickles, completely encloses the fruit until it is ripe, when it splits into 

 four valves. Both kinds of catkins are formed in the axils of leaves of shoots 

 of the same year, the mixed catkins being nearer to tlie apex than the <? ones. 

 The ovules are suspended. The leaves are arranged spirally on vigorous shoots ; 

 they are distichous on the less vigorous lateral shoots. C. vulgaris, from 

 Southern Europe, is cultivated in parks ; it has undivided toothed leaves. 



Order 4. JuGLANDACEiE. Flowers monoecious, the two kinds of 

 flowers being contained in distinct catkins. Each bract bears in its 

 axil a single flower with two bracteoles. The ? flower has usually 

 a perianth : the inferior ovary is dimerous, and encloses a single 

 erect orthotropous ovule. The (^ flowers are usually borne on the 

 bract ; they may or may not have a perianth, and the stamens are 



indefinite (Fig. 389^). The 

 fruit is drupaceous ; the 

 leaves are pinnate, and, like 

 the flowers, they are aro- 

 matic. 



In Juglans the <^ catkins are 

 borne ou the apices of the leafless 

 Fig. 889.— J. Bract of the ^ catkin of Juglans shoots of the previous year, and 

 nigra bearing a flower : p perianth and bracteoles; ^^le few-flowered $ catkins on the 



s stamens ; x axis of the catkin. B ? flower . x xu i r i, ^*„ ^e +v,/> 



' , , , ^ , , ,. apices of the leafy shoots of the 



of the same plant: I bracteoles ; c perianth; n ^ i . i.i 



stigmata (magnified). " same year. The bracteoles of the 



? flowers (Fig. 389 /) {.row up 

 around the ovary. The succulent mesocarp is thin, and ruptures irregularly ; 

 the hard endocarp opens on germination along the line of junction of the two 

 carpels, and then the incurved margins of the carpels are seen as an incom- 

 plete longitudinal septum projecting between the two cotyledons of the embryo 

 which is closely invested by the endocarp. J. regia, the Walnut Tree, is a 

 native of Southern Europe : in North America, J. cinerea and nigra occur; a'so 

 various species of Carya, the Hickory, remarkable for its very hard wood. 



Order 5. MYRiCACEiE. Trees or shrubs ; the flowers, which are 

 diclinous and sometimes dioecious, are arranged in catkins ; perianth 

 absent. The ovary is dimerous and unilocular, with one erect 

 orthotropous ovule. 



Myrica Gale, the Bog-Myrtle, is a shrub occurring on moors. M. cerifero, 

 belonging to North America, secretes a quantity of wax on its drupaceous 

 fruits. 



