1910] BLODGETT—BULBS OF ERYTHRONIUM 353 
The slow growth of the runners made experiments with them 
unsatisfactory when using the centrifuge or klinostat, but the evi- 
___ dence obtained tends to confirm the indifference to gravitation noted 
__ under natural conditions. 
. The lateral displacement of axillary buds, with little subse- 
quent elongation, occurs in species of Gagea (IRMiscH 10). In 
G. minima, G. lutea, and G. pratensis there are short protrusions of 
the bulb rudiment as if about to form a runner, but the elongation 
is not sufficient to burst through the base of the bulb. The sheath 
in which the new bulb is formed is the base of one of the leaves, 
which forms a pouch or pocket about the enlarging bulb rudiment. 
In Tulipa the base of the petiole not only forms the pocket imme- 
diately about the bulb rudiment, but elongates in such a manner 
as to carry the inclosed bud forward into the soil as the terminal 
bud in a hollow runner. This is the type mentioned above as 
occurring in Erythronium albidum and others in respect to the apical 
bud. In each of these cases the bud tends to become deeper than 
its predecessor, but in Allium vineale and A. Scorodophrasum 
(Irmiscx 10) the buds are borne upon independent bases, which 
elongate during the growth of the buds, so that the the buds are 
elevated from the first position and thrust out of the top of the bulb. 
In the cases first mentioned the buds are attached laterally to the 
bulb tissue from which they arise, and are thus unable to rise above 
their insertion, but must descend more or less sharply in the indi- 
vidual species. 
Structure of runners 
The structure of the runner may be understood from the accom- 
‘Panying diagram (text fig. 4). Such a bud as that of Allium 
vineale, which elongates in the region below the insertion of the 
bud scales, would be elevated above its original position; this is 
the normal erect bud. On horizontal rhizomes a bud assumes the 
Position shown in 2 of the diagram at the close of the period of 
elongation. If this position were taken during active progress 
through the soil, a great amount of resistance would have to be 
Overcome in pushing the erect bud forward. This exact arrange- 
ment of parts has not been noticed in nature; but it occurs 
Slightly modified in Erythronium propullans. In this species the 
