PHYLLODIA, ASCIDIA, ETC, 



173 



traversed by ribs, mostly of the parallel-veined kind. In these 

 cases the proper blade of the leaf is commonly abortive or disap- 

 pears ; this substitute, called a PHYLLODIUM (meaning a leaf-like 

 body), taking its place. These phyllodia constitute the whole foli- 

 age of the numerous Australian Acacias. Here they are at once 

 distinguished from leaves with a true blade by being entire and 

 parallel-veined ; while their proper leaves, as the primordial ones 

 uniformly appear in germination, and also later ones in casual in- 

 stances, are compound and netted-veined. They are also recog- 

 nized by their uniformly vertical position, presenting their margins 

 instead of their surfaces to the earth and sky ; and they sometimes 

 bear a true compound lamina at the apex, as in Fig. 227. These 

 Acacias, with the Myrtaceous trees that have leaves with a proper 

 blade which becomes vertical by a twist (294), compose more than 

 half of the forests of New 

 Holland, and give to them a 

 prevailing and very peculiar 

 feature, and an unusual dis- 

 tribution of light and shade ; 

 the cause of which was de- 

 tected by the scrutinizing 

 glance of Robert Brown. 



301. In the Dionsea, or 

 Venus's Fly-catcher, (Fig. 

 228,) the proper lamina, or 

 blade of the leaf, is the ter- 

 minal portion, fringed with 

 stiff bristles, which closes 

 suddenly and with consider- 

 able force when the upper 

 surface is touched. This is 

 borne on a dilated, foliaceous 

 body, which may be held 

 to represent the petiole ; but 

 it is horizontally expanded 



and netted-veined. Still more singular modifications of the leaf are 

 met with in the form of 



302. Ascidia, or Pitchers (Fig. 223-225). These occur in sev- 



FIG. 228. A plant of Dionsea muscipula, reduced in size. 



15* 



