1 14 Oliver —On the Obliteration of 
vegetative organs. The placing of these genera together I can 
but ascribe to that wonderful ‘ instinct for affinities ’ possessed 
by great systematic botanists. As investigation into minute 
plant-anatomy is pushed further and further, this characteristic 
of correctly gauging the true systematic position of a plant 
from external data only is repeatedly seen; thus, to give 
another instance, Scott l * , in his investigations into the distribu- 
tion of laticiferous tissue in Euphorbiaceae , finds himself able 
to confirm on purely histological grounds Bentham’s separa- 
tion of certain tribes on ordinary macroscopic data. 
This investigation has been conducted entirely on dried 
herbarium-material, but I have always been able to confirm 
my results by the examination of a great number of specimens 
which have been collected at various epochs by Bond, Banks, 
Hooker, Harvey, Lyell, Moseley, and others. I have material 
taken as long ago as 1774 up to as recent a date as 1874 by 
the ‘ Challenger 5 expedition. I wish to take this opportunity 
of thanking Mr. J. R. Jackson of the Kew Museums, and 
Dr. Carruthers and Mr. E. G. Baker of the Natural History 
Museum, all of whom have very liberally put material at my 
disposal. 
My mode of procedure has always been as follows : — The 
dry pieces were placed in water for several hours — sometimes 
even twelve — during which time they absorbed very much, and 
swelled up often to four times their original diameter when 
put in. They were then placed in weak spirit, and after a few 
hours stay in this they were in very good state for preparing 
sections. The material was now transferred to stronger spirit 
and kept in this way any length of time. 
I am fully aware that it may be urged as an objection 
against my results that these callus-plates are simply aggrega- 
tions of a peculiar mucilage artifically induced by my method 
of softening dry herbarium-material, seeing that I have not, as 
yet, confirmed them with fresh material. To this I need only 
1 D. H. Scott, Articulated Laticiferous Vessels in Hcvea , in Linnean Soc. 
Journal, Bot. Vol. xxi. p. 572. 
