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Igor] THE LIFE HISTORY OF ERYTHRONIUM 371 
Columbus, most of the leaves have wilted away. The plant, 
therefore, is rarely much more than two months above ground. 
Erythronium is an ideal example of the retreating bulb. The 
retreating stems are axillary buds which are carried downward 
by growth and division of the cells above and beside the apex of 
the bud. zg. 7 is a section of such a young bulb, and the dotted 
region shows where active cell division is going on. The devel- 
opment of these offsets has been described several times recently, 
so that it is unnecessary to refer to the subject further. 
The deep burrowing is probably not only to place the plant 
in deep soil, but also to keep the flower protected in the warm 
earth during winter. The advantage of retreat for nine or ten 
months underground must be decided, and the causes for the 
habit complex. The leaves come out before there is any danger 
of shading from other plants, and before the leaves of the higher 
stratum of trees shut out the light. The plant is thus well 
adapted to forest conditions. 
KARYOKINESIS IN THE BULB. 
The division stages in the bulb were studied in order to trace 
out the development of the spindle. The resting nuclei usually 
have a rather dense chromatin network with numerous nucleoli 
imbedded in cavities (fig. 2). Often the nucleoli take on fan- 
tastic shapes, probably due to budding and division. Some of . 
these are shown in fig.3,a,6,c, etc. Farther up, beyond the 
division region, the nuclei elongate in the cells of the develop- 
ing vascular bundles. After the continuous spirem begins to 
form, two caps of fibers appear on opposite sides of the 
nucleus, which are the incepts of the future spindle. These 
are dome-shaped or cone-shaped in appearance, and often end 
in definite granules around which there is sometimes a system 
of radiations (fig. 5). Similar incipient spindles, but farther 
advanced, are shown in figs. 6, 7,and 8 In fig. 7 the chroma- 
tin granules are plainly visible in the spirem, forming a single 
chain. fig. 9 represents a loose mother skein some time before 
the formation of the mother star. The spindle at this stage is 
