88 R. H. CAMBAGE. 



In many species the primary leaf is quite glabrous, but 

 in others the stalk, or in fewer cases the rachis, may be 

 pilose, and the margins of the leaflets ciliate. Leaflets 

 commonly number from two to five pairs, but the number 

 is not constant for any species and sometimes only one 

 pair may appear on a species which usually has two. A. 

 accola may have up to eight, and A. Bidivilli nine pairs. 



The leaflets are generally very shortly petiolate, the 

 petioluie varying from about '2 mm. to 1 mm. long, and they 

 are usually opposite, but some are alternate. The terminal 

 pair are generally opposite, and the rachis excurrent. A 

 common shape of the leaflets is oblong-acuminate, some- 

 times mucronate and oblique, though they may be even 

 cuneate. 



There is considerable similarity in the venation of the 

 leaflets of most species. First there is the midrib extend- 

 ing somewhat obliquely along the length of the leaflet and 

 nearer to the upper than the lower margin. Next between 

 the lower margin and the midrib there is, in many species, 

 a second longitudinal vein, radiating from the base of the 

 leaflet, and extending, in part, almost parallel to the mid- 

 rib until it reaches near the lower margin about or above 

 the centre. There is also a system of reticulating veins, 

 but owing to the thickness of the epidermis this is often 

 indistinct. (Fig. 1.) 



The disposition of the two longitudinal veins, in many 

 species, is suggestive of the possibility that the present 

 form is a modification of a leaflet which was formerly 

 triplinerved. This suggestion is supported by the tripli- 

 nerved venation of the cotyledons of such species as A. 

 suaveolens and A. aneura, but requires to be further 

 investigated. 



Out of about 400 seedlings taken from about 60 species, 

 only two cases so far have been noticed where the third 



