CHAP. 7T. LEAVES. 109 



This kind of leaf has not been before clistingnished: it may 

 be considered intermediate between those without veins and 

 those in which primary veins are first apparent. The veins 

 are e^jual in power to the proper veinlets of leaves of a higher 

 class. 



3. Straight-veined [rectivenium) . In this the veins are en- 

 tirely primary, generally very much attenuated, and arising 

 from towards the base of the midrib, with which they lie 

 nearly parallel: they are connected by proper veinlets; but 

 there are no common veinlets. The leaves of Grasses and of 

 Palms and Orchideous plants are of this nature. This form 

 has been called by Link parallcli and convergenti-nervosum^ 

 according to the degree of parallelism of the primary veins; 

 and to these two he has added what he calls venuhso-nervosumy 

 when the primary veins are connected by "proper veinlets; 

 but as this is always so, although it is not in all cases equally 

 apparent, the term is superfluous. Ach. Richard calls this 

 form laterinercium^ and De CandoUe rcctinervium ; from which 

 I do not find it advisable to distinguish his rnptinervium, 

 which indicates the straight-veined leaf, when the veins are 

 thickened and indurated, as in the Palm tribe. 



4. Curve-veined {curvivenium) . This is a particular modifi- 

 cation of the last form, in which the primary veins are also 

 parallel, simple, and connected by unbranched proper vein- 

 lets ; do not pass from near the base to the apex of the leaf, 

 but diverge from the midrib along its whole length, and lose 

 themselves in the margin. This is the folium hinoideum 

 and venuloso-hinoideum of Link, the f. j)enninei^ium of A. 

 Richard, and the f. mrvinemium of De Candolle. It is com- 

 mon in Scitamineae. It is not improbable that both this and 

 the last ought to be regarded as peculiar modifications of 

 petiole (a kind of phyllodia), rather than as true leaves analo- 

 gous to those next to be described. 



5. Netted {reticidatum). Here the whole of the veins that 

 constitute a completely developed leaf are present, arranged 

 as I have above described them, there being no peculiar com- 

 bination of any class of veins. This is the common form of 

 the leaves of Dicotyledons, as of the Lilac, the Rose, &c. It 

 is the folium venosum of Linnaeus, the f. indirecte venosum 



