STRUCTURE.] VARIETIES OF VENATION. 267 



confounded with the straight-veined leaf, from which it 

 may in all cases of doubt be distinguished by the rami- 

 fied veins that connect the ribs. This is a very material 

 difference, which has never been properly explained. 

 Linna3us and his followers confound the two forms ; but 

 modern writers separate them : although it must be 

 confessed that it is difficult to discover their distinctions 

 from the characters hitherto assigned to them. Link 

 calls these leaves /. nervata, A. Richard /. basinervia, 

 and De Candolle /. triplinervia and /. quintuplinervia. 

 If a ribbed baf has three ribs springing from the base, 

 it is said to be three-ribbed (tri-costatwn, trinerve of 

 authors) ; if five, five-ribbed, and so on. But if the ribs 

 do not proceed exactly from the base, but from a little 

 above it, the leaf is then said to be triple-ribbed (tripli- 

 costatum), as in the Helianthus. 



7. Falsely ribbed (pseudocostatum] , is when the curved and 



external veins, both or either, in a reticulated leaf, 

 become confluent into a line parallel with the margin, as 

 in all Myrtleblooms (Myrtacere). This has not been 

 before distinguished. 



8. Radiating (radiatum], when several ribs radiate from the 



base of a reticulated leaf to its circumference, as in 

 lobed leaves. This and the following form the/, directe 

 venosum of Link : it is the/, digitinervium of A. Richard. 

 Hither I refer, without distinguishing them, ihef.peda- 

 linervia, palminervia, and peltinervia of De Candolle; the 

 differences of which do not arise out of any peculiarity 

 in the venation, but from the particular form of the 

 leaves themselves. 



9. Feather-veined (pennivenium) , when the venae primaries of 



a reticulated leaf pass in a right line from the midrib to 

 the margin, as in Castanea. This has the same relation 

 to the radiating leaf that the curve-veined bears to 

 the straight-veined; it is the folium penninervium of 

 De CandoUe. 



10. Hidden-veined (introvenium) . To this I refer all leaves 

 the veins of which are hidden from view by the paren- 

 chyma being in excess, as in Hoya, and many other 



