nr-ENOGAMiC VEGETATTOX OF RODlUOrEZ. 28 



Hab, In vallibus montibusque a litore retnotis crescit. Nom. vulg. 

 Vacoa Chevron. 



A species belonging to the ITtilis group, and by some (perhaps 

 hybrid) forms approaching very near P. Iieferocarpus, but easily 

 distinguished when typical by habit, the narrow drooping leaves, 

 and the large drupes with rounded apices. 



A very marked feature in the Eodriguez flora, and one worthy 

 of special notice, is the variability in size, form, and habit exhi- 

 bited by the leaves of many plants at diflFerent stages of growth. 

 The variation is confined almost absolutely to small trees and 

 shrubby plants, occurring in seventeen species, all of which are 

 either endemic or Mascarene, one only extending into Africa. The 

 young plant, in these heterophyllous species, produces leaves of a 

 lower stage of development tlian the adult; and as the individual 

 grows older the leaves successively developed are more like those 

 of the mature tree, until at a certain age only the form of leaf 

 typical of the adult is produced. But in an adult plant, should 

 any adventitious shoots be given off from the stem below its first 

 branching, these have the juvenile, not the adult form. The he- 

 teromorphism varies greatly in degree and kind; but each species 

 presents variations always of the same kind. Whether all the 

 species of the same genus on the island exhibit, when they vary, 

 the same type of heterophylly, I had no opportunity of determi- 

 ning ; certainly representative species in the adjacent islands do 

 not always do so. The phenomenon is confined to no special 

 family ; but it is worthy of note that of Eubiacese no less than 

 four species exhibit it. 



"We may best understand the variations in size and form by 

 considering that there are three types of variations. 



In the first the diff'erence between the leaves of the young 

 and the adult is mainly one of size, the relative proportion of 

 length and breadth of lamina being the same in both ; and in each 

 the margins of the lamina are usually entire. Sometimes the 

 parenchyma is deficient at the margin in the juvenile, so that it 

 is slightly spiny, this character gradually disappearing in the adult. 

 This kind of heterophylly is observed in three species — Zudia se^- 

 siliflora, Fernelia luxifolia^ Carissa Xylopicron, 



The second kind of variation results from the non-development 

 in breadth of the leaves of the young plant, usually accompanied 

 by a great increase in length, the relative proportion of length 



