158 
Transactions of the 
TMi, nthly Microscopical 
L Journal, March 1, 1869. 
duced, at right angles with it, and alternate with the Ven^ pri- 
marise, smaller veins, which may be considered imperfect Vense 
primarim, and may not improperly be named Vense costales. The 
Venm primarise are themselves connected by fine veins, which anas- 
tomose in the area between them. These veins, where they imme- 
diately leave the Venm primariw, I call Venulse proprise; and where 
they anastomose, Venulse communes!' 
The feather-veined leaf is thus described by the same author : — 
" When the Venm primarise of a reticulated leaf pass in a right line 
from the midrib to the margin " — as in Gastanea (Sweet chestnut) 
or Gorylus avella^ia (Hazel). Plate Y. 
We have now to consider how, amongst the diversified and com- 
plex forms assumed by leaves, one and the same typical leaf struc- 
ture, arranged in a variety of ways, is clearly discoverable in them 
all. This typical form may be either the netted or the feather- 
veined leaf. Let us take the latter, by way of illustration, and 
trace it through the seven series of leaves in which we think its 
presence is capable of proof, by a direct appeal to the leaves them- 
selves. 
1. The feather-veined leaf exists in its simple, entire, isolated 
state, as in the Spanish chestnut (Gastanea), or the Hazel {Gorylus 
avellana). Plate Y. 
2. It is repeated in the form of separate leaflets, which radiate 
from the summit of the petiole (leaf-stalk), as in Horse-chestnut 
{Msculus hippocastanum). Plate Y. 
3. It is repeated in the form of leaflets which radiate from the 
summit of the stalk, and of which some are separate, others united, 
as in Blackberry (Buhus fruticosus). Plate Y. 
4. It is repeated in the form of leaflets which radiate from the 
summit of the petiole, and which are all united at their edges, half- 
way towards their margin, as in Sycamore {Acer Pseudo-platanus). 
Plate Y. 
5. It is repeated in the form of separate leaflets, arranged in 
rows on the sides of an elongated petiole, as in Sumach [Bhus 
typhina). Plate Y. 
6. It is repeated in the form of leaflets, arranged in a row on 
either side of an elongated petiole, some of which are separate, 
others united, as in the metamorphosed leaves of Baspherry {Buhus 
Iddeus). Plate Y. 
7. and lastly. It is repeated in the form of leaflets, arranged in 
a row on either side of the petiole, and which are all united at their 
edges, to a greater or less extent, towards their margin, as in 
Gineraria maritima. Plate Y. 
When arranged in conformity with the usual nomenclature, this 
series resolves into — 
