July 15, 1921 
Effect of Crowngall Inoculations on Bryophyllum 595 
originating in some extremely vascular tissue is itself very vascular, much 
more so than one originating in a non vascular tissue, although the 
latter always contains some vessels (tracheids) just as any wound repair 
tissue does. 
To return now to Bryophyllum, when suitable inoculations are made 
under a dormant bud-—that is, immediately under a petiole—the devel¬ 
oping tumor not only stimulates the bud to develop into shoots, as may 
be seen in Plate 101, but sometimes even causes, like the disease in the 
peach tree called the peach yellows, a secondary set of branches to 
appear on such shoots, as may be seen under the arrows in Plate 101. 
Here the tumor-stimulated shoots are the only axillary shoots on the 
plant. Often the tumor tissue subsequently invades the swollen base of 
such a shoot. 
On the contrary, when the inoculations are made directly into the 
leaf axil—that is, into the dormant bud and into tissues immediately 
surrounding it—centers of infection and of active growth begin around 
the needle pricks, and these disrupt the bud in various directions, 
widely separating its fragments, as may be seen in thin sections under 
the microscope; and subsequently these fragments are just as certain to 
feel the tumor stimulus and to develop as is the whole bud in the pre¬ 
vious case, only, the food supply and water supply being divided and 
limited by distortion and rupture of the vascular bundles, the result will 
be the development in the axillary tumor of several to many stunted 
shoots or mere buds, rather than one or two strong shoots. This is 
illustrated in Plates 102 and 103, which are back and front views of the 
same inoculated plant. 
This stimulus, moreover, contrary to Mr. Levine, not only causes axil¬ 
lary buds of Bryophyllum to germinate, but also leaf-notch buds. To 
have made his test of any value (conclusion 2), Mr. Levine should have 
inoculated leaves while still on the plant and not after removal, when 
most of the leaf-notch buds will grow indiscriminately whether inocu¬ 
lated or not. Also they should have been young leaves. When done 
in the right way, the buds, stimulated by crowngall, develop, and no 
others, as may be seen in Plate 104, where out of about 400 dormant 
buds situated on the margins of the 26 leaves only those on 2 inoculated 
leaves have developed into shoots; and even here, if I had made my in¬ 
oculations only on well-developed leaves some or all of my results might 
have been negative, as happened on one of the lower leaves of this same 
plant. That here the growth of the dormant buds into shoots is attrib¬ 
utable to the inoculations in their vicinity and to nothing else is plain, 
because leaf-notch buds do not develop at all on undisturbed young 
shoots. In old plants they grow freely out of the leaf notches of old 
leaves which are still green and very firmly attached to the stem—that 
is, not pathological—but the order of their development is different— 
that is, they first appear on the basal leaves and gradually extend to 
