GoRHAM; on the UmbeUifercB. 15 



presenting one kind of venation, anotlier part of the same 

 leaf another kind of venation. Take, for example, the com- 

 mon sow-thistle (Sonchus oleraceus) ; the lower portions of 

 this leaf are true feather veinal, while the upper portion, on 

 the other hand, is as truly notted. This leaf, therefore, fur- 

 nishes us with an example of the transition or connecting 

 link between these two kinds of veining, and its position 

 when classified is mtermediate. 



Many examples of this and analogous transitions were fur- 

 nished to the late Dr. Lindley, who expressed his obligations 

 to me in the course of a correspondence. 



There is, be it observed, no paucity of leaves in the county 

 of Kent. I had abundant means, therefore, at my command 

 for specimens. Neither were any pains spared to make a 

 thorough investigation of them, so that, after collecting and 

 classifying a goodly number in strict accordance with the 

 received nomenclature, my labours for the time seemed to 

 have come to an end, and I rested satisfied that, so far as the 

 venation of leaves was concerned, 1 at least knew nearly all 

 about it. 



But when recently, and after a lapse of some twenty-two 

 years, I began for a special purpose to re-examine the distri- 

 bution of the veins in leaves, and when I found a peculiar 

 vein occupying a perfectly different position in the leaf to 

 that of any heretofore seen by myself or, so far as I could 

 find, described by others, it seemed to me that the position 

 and course of such a vein were worthy of notice and descrip- 

 tion. Hence this present communication. 



It may be as well here to premise a few remarks as to the 

 simple exj)eriments by which the result of my inquiries were 

 arrived at. In the first place, the leaves themselves were 

 pressed, well dried, and then movmted between two slips 

 of glass. No one should ever grudge the time spent in care- 

 fully putting up an object for the microscope, for a well- 

 mounted object affords such facilities for its examination that 

 the specimen itself becomes doubly valuable. The glasses are 

 three inches square, this size being found sufficiently large 

 to hold a leaflet which is placed between them, and the edges 

 are then secured with gummed paper. Leaves thus treated 

 will keep for years, retaining their integrity, while the veins 

 become bold and sharp, and stand out in stronger relief as 

 they become drier by age. 



With regard to the lenses used for examining the veins in 

 leaves, I have found a magnifying power of about twelve 

 diameters amply sufficient to show every vein from the mid- 

 rib in the centre to the finest reticulations in the margin. A 



