1905] McCALLUM—REGEN ERATION IN PLANTS 259 
apical buds of the other. Indeed if any bud be selected, and the 
stem cut off just above it, the bud develops; but if the stem be cut 
off just below this same bud, so as to leave it at the base of the piece, 
it will not develop. Two pieces of Salix stem were selected as nearly 
alike as possible, and of exactly the same age. At about the center 
of each several buds, all alike, were selected; and each piece was 
cut in two, one so that these buds remained at the apical end, and 
the other so that they were at the basal end. In the former they 
developed and in the latter they did not. Experiments could be 
multiplied indefinitely to show that all the buds along the stem are 
equally able to develop; and whether any particular one does or not 
depends on whether the piece be cut so as to leave it near the apical 
or basal end. 
The development of any plant involves the growth of a few and 
the suppression of many potential structures; and this is true not 
only of the vegetative buds, but also of other parts. In the ovary 
of Tilia, for example, ten ovules are present and may all be fertilized; 
but very soon nine cease activities and one only continues to form 
- embryo. A similar event occurs in Pinus and other plants. Were 
it merely a question of food, a fierce struggle would ensue among the 
developing embryos, and some at least would continue for a long time 
in a more or less starved condition. In Pinus practically all the 
embryos except one stop growing, while all about them are disinte- 
grating tissues liberating food materials, some of which must pass 
by, or even through the arrested embryos to get to the one that con- 
tinues growing. The formation of the embryo in many plants is 
‘ccompanied—or immediately followed—by the development of 
other parts, often more or less distant, e. g., the large fruit of the 
melon, an event that we cannot attribute to any increase of nutrition 
resulting from the developing of the embryo. 
= to the growth at the meristematic growing point 
ba. “a5 special regions which remain meristematic, as the cam- 
of th i Slay for vegetative development is retained by per 
ox. ae tissues in various parts of the plant body. Sits 
a ‘bi s > the embryonic tissue differentiate into other ee 
ie us ome er functions they may still remain ensheyems = 
aining complete reproductive capacity. So we 
