454 BOTANICAL GAZETTE [JUNE 
that there are no anatomical or microchemical differences in the 
surface cells of the two sorts of leaves, one is led to infer that the 
differences in the quantities of water (and solutes) drawn up 
through the xylem into galled and normal leaves furnish the 
reason for the differences in the amounts of conducting tissue as 
shown by the annual rings. 
In 1893 Jost’ concluded from a series of experiments which 
he made on seedlings and on certain older woody plants, that 
the development of the vascular bundles is very intimately con- 
nected with the development of the leaves. His experiments 
consisted in part in removing the leaves when the seedlings were 
very young or in forcing leaves to develop from the bud in 
darkness. Any experiment which involves amputation or other 
serious injury is obviously to be used only very guardedly as the 
basis of conclusions regarding the relations of parts to each other. 
An experiment involving the amputation of a leaf shows two 
things: the effect of the wound and the effects due to abuses 
of the leaf and of the processes normally going on in it. 
Which is the predominant influence no one knows, and whether 
the result is not a resultant rather than the swum of two 
different effects is also unknown. It is conceivable that a 
reduction of the leaf surface, or the suppression of the whole 
organ without wounding, might have a different effect from 
cutting off a leaf. This Jost tried by causing leaves to develop 
in darkness from the bud. But here again more than one thing 
is involved. The formative and directive influences of light as 
well as its influence on the photosynthetic and other processes 
connected with nutrition going on in the leaf, are all eliminated. 
Though no wound is made, the result may again be a resultant 
rather than the swm of the factors concerned. The results which 
Jost obtained agreed, however, in that, whether the leaves were 
removed or were reduced by being grown in darkness, the 
vascular bundles were much smaller. Jost used among other 
plants two species of Pinus. 
If we now compare Jost’s results with ours, we see that they 
sJost, K., Beziehungen zwischen Blattentwickelung und Gefiassbildung in der 
Pflanze. Bot. Zeit. 51: 89-138. 1893. 
