84 THE FLORIST AND 
monocotyledons, in wliich the vascular bundles lie scattered through the 
whole stem, and no definite cambium layer exists, the conditions are far 
more unfavorable. It is true, according to De Candolle's account, that 
Baumann, of Boll wilier, succeeded in grafting Draccena ferrea on D. term- 
inalis ; but the scion died after the first year. The experiments, indeed, of 
Caldrini on grafting Grasses had a more favorable result, for he succeeded 
in grafting even species of difierent genera, such as Rice upon Panioum 
crus gain. This result may be explained by the fact that in Grasses the 
lower part of the internodes enclosed in the leaf-sheath remains for a long 
time soft and succulent. A second and indispensable condition in grafting 
is a great similarity of the stock and scion; they must not only be nearly 
allied botanically, but be much alike in the composition of their sap. Yet 
although the possibility of grafting plants upon each other depends, in gen- 
eral, upon their close natural relationship, still many anomalies occur. In 
most cases different species of the same genus may be grafted on each other 
or even in some instances species of nearly-allied genera, as, for example, 
Pears on Quinces, or White Thorn {Cratcegus oxyacantha), or the snowy 
Mespil [Amelanehier vulgaris), while the common Lilac takes on the Ash 
tree and FMllyrea latifolia, the Olive on the Ash tree, and the Spanish 
Chestnut on the Oak. Nevertheless, on the other hand, no union, or at 
least no permanent union, can be secured, where there is a far closer botan- 
ical affinity, as, for example, between the sweet Chestnut and the Beech, or 
the Apple and the Pear." 
To this effect writes Mohl in that admirable treatise of his on the cells of 
plants, the best work on Vegetable Physiology in any language. We quote 
it because, although he merely states notorious facts, yet the manner of put- 
ting them may be new to some of our readers. Let us see how far it goes to 
settle the matter in dispute among our correspondents. 
It is, we think, incontestible, that although two plants of difierent species 
may be made to form a mutual adhesion by the process of grafting, yet that 
such adhesions are seldom if ever permanent, or even advantageous to the 
vigour of the scion. It is only when varieties of the same species are 
worked on each other, that a perfectly sound and durable union is effected ; 
and not always even !;then, as we see when a fast growing Apple tree is 
grafted upon a diminutive variety, such as the Paradise. If the union is to 
be perfect and the double or grafted plant to be in all respects as healthy 
as either of its parents the two must grow at the same rate, must have their 
sap in action at the same instant of time, and the quality of their secretions, 
be they what they may, must be identical. This happens when Pear trees 
