368 BOTANICAL GAZETTE [NOVEMBER 
asin Tulipa. The additional runners when present, and all three 
in E. americanum, are developed from the elongation of the outer 
scale of the bud, the inner scale and the apical dome forming the 
terminal bud of such a runner. 
The vascular connection between the stem apex and the point 
of insertion of the runner is to be considered cauline, the rest of 
the runner tissue as foliar and apical. The structure of the runner 
in E. americanum is that of an anatropous bud, the outer surface 
of its external scale being fused with the upper surface of the support- 
ing stem; the latter maintains vascular connection between the 
base and the apex of the structure developed. The zone of growth 
of the fusion structure is located as in normal rhizomes, close to the 
tip of the structure; both the scale and the cauline tissue take 
part in the elongation. ‘ 
The mature plants form the floral shoot from the stem apex, the 
new bulb being developed from a bud, at the base of the shoot. The 
stem apex of the new bud forms the next flower, and the bulb is re- 
newed in turn from a bud axillary to the inner scale of the bulb rudi- 
ment. The bud in the axil of the outer scale usually dies without 
developing. 
Using the runner habit as the basis of comparison, the soo. 1S 
divided into two groups, one occurring typically at low elevation, 
and producing two or three slender runners from short bulbs, the 
other at higher elevation and forming but one runner and develop- 
ing into slender bulbs. A form intermediate between the two 
occurs in western Kansas and Nebraska. An aberrant form occurs 
in a restricted locality in Minnesota, having a lateral runner 
developed from a bud in the axil of a foliage leaf. 
The interval between germination and flowering on the pat t of 
an individual is at least six years. This minimum is liable to 1~ 
definite increase under average conditions, by the interpolation of 
additional immature bulbs because of the formation of the runnet 
bulbs no deeper than the parent bulb, or by the suppression of 
runners in a particular year. 
The distribution of the species points to the Pacific coast as 
the probable home of the genus, the present distribution being 
the result of migration along lines connecting the habitats of the 
