910] BLODGETT—BULBS OF ERYTHRONIUM 351 
of the external scale is united to the subtending portion of the 
bulb. As the buds begin their development, the first growth is 
eccentric and pushes the base of the bud outward from its first posi- 
tion, leaving the bottom of the bud free from contact with other 
tissues. Subsequent growth on the part of the bud is chiefly 
located in a zone about the base of the scale, close to the insertion 
of the inner scale upon the base of the bud. As the point at which 
the bud is united to the bulb tissue is above the zone of growth, 
the growing zone tends to push the base of the bud away from its 
original position and downward into the soil, as was the case in the 
beginning of the dropper. This elongation is confined almost 
entirely to the outer scale, the inner scale and the inclosed stem 
Fic. 3.—Space relations of buds in immature bulb of E. americanum: 1, stem 
apex; 2, inner axillary bud; 3, outer axillary bud; X1o. 
apex being carried along passively, as the terminal bud in the 
runner (cf. fig. 13). The runner is thus formed by the elongation 
of the outer scale of the bulb rudiment, and in the case of the 
apical bud and the inner axillary one, they burst through the 
inclosing base of the petiole when the base of the bulb has been 
penetrated. In these runners the scale is definitely organized 
in the bud, before any elongation begins, and the base of the 
foliage leaf takes no share in the formation of the runner, as did 
the base of the cotyledon in the seedling dropper. In other species? 
the sheathing base of the foliage leaf contributes to the developing 
runner, as in the case of the cotyledon and dropper. The elonga- 
_ Uon in this type of runner is the same as that in Tulipa (ROBERT- 
‘ E. albidum for example. 
