266 VARIETIES OF VENATION, [BOOK i. 



this form latermervium, and De Candolle rectinervium ; 

 from which I do not find it advisable to distinguish his 

 ruptinervium, which indicates the straight-veined leaf, 

 when the veins are thickened and indurated, as in the 

 Palm tribe. Straight -veined leaves occur generally in 

 Endogens, and, slightly modified, are one of the charac- 

 teristic marks of Epacrids. Some Botanists regard 

 leaves with this kind of venation as consisting of petiole 

 only ; but I am unacquainted with any fact which con- 

 firms this view. 



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 veinlets ; 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/, penninervium of A. Richard, and the /. curvinervium 

 of De Candolle. It is common in the whole Musal 

 alliance, and is unknown except among Endogens. It 

 is supposed by the last-named Botanist that this also 

 ought to be regarded as a peculiar modification of petiole 

 (a kind of phyllode), rather than as a true leaf analogous 

 to those next to be described. 



5. Netted (reticulatum) . Here the whole of the veins which 



constitute a completely developed leaf are present, 

 arranged as I have above described them, there being 

 no peculiar combination 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 /. indirecte venosum of Link, the /. mixti- 

 nervium of A. Richard, and the /. retinervium of De 

 Candolle. If the external veins and marginal veinlets 

 are conspicuous, Link calls this form combinate venosum; 

 but if they are indistinct, he calls it evanescent e venosum. 



6. Ribbed (costatum). In this three or more midribs proceed 



from the base to the apex of the leaf, and are connected 

 by branching primary veins of the form and magnitude 

 of proper veinlets, as in Melastoma. This must not be 



