13*2 
ORGANOGRAPHY. 
BOOK I. 
necessary ; but, if they be employed, the termination nervia 
must be changed to venia. 
2. Equal-veined [(vqualivenium) , when the midrib is per- 
fectly formed, and the veins are all of equal size, as in Ferns. 
This kind of leaf has not been before distinguished : it may 
be considered intermediate between those without veins and 
those in which primary veins are first apparent. The veins 
are equal in power to the proper veinlets of leaves of a higher 
class. 
3. Straight-veined [rectiveniujn) . 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 Orchidaceous plants are of this nature. This form 
has been called by Link paralleli- and convergenti-nervosum, 
according to the degree of parallelism of the primary veins ; 
and to these two he has added what he calls venuloso-nervosum^ 
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 laterinervium^ and De Candolle rectinervium ; from which 
I do not find it advisable to distinguish his ruptinervium^ 
which indicates the straight-veined leaf, wdien 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 liinoideum and 
venuloso-hinoideum of Link, the f. penninervium of A. Richard, 
and the f. curvinervium of De Candolle. It is common in 
Zingiberaceae. It is supposed by the last named Botanist that 
both this and the last ought to be regarded as peculiar modi- 
fications of petiole (a kind of phyllodia), rather than as true 
leaves 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 
