162 
Transactions of the 
[Monthly Microscopical 
Journal, March 1, 1869. 
It may be well to notice a little more particularly in this place 
the changes which take place in the size, number, and distribution 
of the veins in these regions (C S, diagram A), where the junction 
of the leaflets is effected ; for whether in metamorphosed or in lobed 
leaves, the plan will be found identically the same. We notice, then, 
that the primary veins in some instances become very small, often 
increased in number, and that, after travelling in their accustomed 
course to about the middle of the region, they anastomose either 
directly or irregularly with those from the opposite side. In other 
cases they will be found nearly entirely obliterated to the naked eye, 
so that this portion of the leaf presents a smooth appearance, and 
leathery texture, nearly destitute of veins, and altogether different 
from the rest of the leaf. They vary, too, as the normal leaflet is 
netted or feather-veined ; and, what is particularly worthy of notice, 
if the ribs diverge at a large angle, more of the normal venation is 
left in this region, clearly showing that it is to the junction of the 
vessels that the altered appearance is to be attributed. This is 
exemplified also, more or less, in all lobed leaves. It becomes 
difficult, therefore, to assign a cause for such a remarkable anomaly 
recurring regularly and alternately throughout their area, if it 
cannot be referred to this modification which takes place in the 
veins from the junction of adjacent leaflets. 
From this aspect, the metamorphosed leaf becomes an inter- 
esting study to the botanist. It is not that insignificant sport of 
Nature which is to be disregarded. A friend of mine, on having 
such a leaf shown her, exclaimed, "Don't show me that deformed 
thing; it has grown against a wrong wall, and is all lop-sided." 
Yet that very leaf contained, as I believe, the key which was capable 
of deciphering the structure of the lobed leaf. 
It is far from my wish to assign an undue prominency to these 
metamorphosed leaves ; yet the more attentively they are examined, 
the more clearly will it appear that they are related, on the one 
hand, in their separate leaflets, to compound leaves, and, on the 
other, in their united leaflets, to lobed ones. They furnish us, there- 
fore, with a transitional series, forming the bond of union between 
two classes which have hitherto been separated by a pretty wide 
line of demarcation, but which, nevertheless, are thus shown to be 
related by natural affinity. 
It was intended to illustrate this portion of the paper by a 
series of figures from impressions taken direct from the leaves them- 
selves, and prepared expressly for the purpose. As their publi- 
cation, however, would have involved much time and labour, I have 
restricted myself to a few selected from the series, and which, from 
being of rare occurrence, or fine specimens of those which are more 
common, will be found sufficient to illustrate what is intended. 
They are all of them examples of the union of two leaves into one, 
