596 
Journal of Agricultural Research 
Vol. XXI, No. 8 
those farther up. In Plate 104 they have appeared on two leaves in 
the middle of a young shoot (uppermost leaves at time of their inocula¬ 
tion) and on these only. Many controls, and also observations extending 
over a period of several years, teach me that this unusual development 
of the leaf buds on an otherwise undisturbed young plant can be attrib¬ 
uted only to the stimulus of the neighboring marginal tumors; and, con¬ 
sequently, the response of totipotent cells in Bryophyllum calycinum is 
not different from that of similar cells in other plants. 
There remains to consider what will happen when the infected needle 
is thrust directly into leaf-notch buds rather than into their vicinity. 
Mr. Levine says it results in the formation of a crowngall without leafy 
shoots (conclusions 1 and 5). Plates 105 to 108 are a sufficient reply 
to this, although they represent only a small part of the results ob¬ 
tained. Here single needle thrusts were made directly into dormant 
leaf-notch buds (toward the top of the plant), usually on one side of 
the leaf only; 1 arid in nearly every case shoots as well as tumors have 
developed, and some of the small, slow-growing tumors bore several 
shoots and roots (35 roots in PI. 108). I had many cases like this where 
shoots developed only from the inoculated notches, other buds on the 
same leaves remaining dormant. Shoots taken from single inoculated 
leaf notches a month earlier than Plate 105 (which is reduced) are shown 
enlarged live times on Plate 106. Here the small tumors at their base 
can be seen very distinctly. It will be observed also that the neigh¬ 
boring uninoculated notches are free from shoots. Later both the 
shoots and the tumors became larger. On the small stimulated shoot 
in at least two cases (PI. 107) the buds in its lower leaf axils (under the 
arrows) also pushed just as in the shoots of Plate 101 and others in 
that series. 
Most of the crowngalls produced on midribs of Bryophyllum calycinum 
are free from leafy shoots. They are free, however, not for the reasons 
assigned, but because totipotent cells are rather rare in the midribs of 
this plant, which has sent most of them to the edges of the leaf. Only 
rarely, therefore, might one expect the infected needle to reach a group 
of such cells. That crowngalls containing shoots and roots may be pro¬ 
duced by midrib inoculations on Bryophyllum is sufficiently evident from 
Plates 109 and no. 
Totipotent cells occur abundantly in the midribs of tobacco, tomato, 
begonia, and pelargonium, but it does not follow that they occur in the 
same abundance in the midribs of all plants, and especially not in those 
of a plant as peculiar as this one. Where we know beyond peradventure 
1 This was probably not done in the best way to induce a breaking up of the bud tissue, since the 
needle was not thrust from the margins inward but from some distance inside the margin outward 
through the leaf parenchyma, parallel to the leaf surface, until it was judged that the bud had been 
reached, a matter always in some doubt because of its invisibility and small size. Three distinct 
shoots are the most I have seen develop from such an inoculation, but undoubtedly the bud can be 
ruptured so as to produce a much larger number of shoots. 
