Robertson. — The ‘ Droppers' of Tilipa and Erythronium. 437 
possesses a well-marked dropper ; in the succeeding years, however, the out- 
growth is so rudimentary as scarcely to deserve the name. The structure 
of the bulb closely resembles that of the Tulip, and the non-flowering plant 
produces annually a single foliage leaf. Asa Gray 1 refers to the ‘ sub- 
terranean runners ’ of E. americanum and E. albidum , and figures another 
species E. propullans , in which a similar structure arises from a point some 
little distance above the parent bulb. It would be interesting to know what 
the exact morphology is in this case. F. H. Blodgett 2 gives a very telling 
series of figures of E. americanum , illustrating the five-year cycle from 
seed to flowering plant, and showing the amount of dropping that occurs 
each season. My Figs. 7 and 8 show two stages in the development 
of a young dropper in this species. 
I have examined the seedling structure of another species, E. grandi- 
florum , by means of serial sections through the transition region of a 
seedling nineteen days old (Fig. 10). Miss Sargant 3 has already mentioned 
that E. Hartvoegi has three bundles in the cotyledon which form a triarch 
root according to the first type of transition described by V. Tieghem. 
In one of the two seedlings of E. grandiflorum which I sectioned, the 
cotyledon near its base contained a midrib with two laterals, and imme- 
diately inside the midrib there was a small inverted bundle (Fig. 9 b). 
The laterals and the small inverted bundle pass down directly into the 
dropper and have no bearing on the symmetry of the root. The phloem 
mass of the midrib runs straight down to form one of the phloems of the 
triarch root. The xylem of the midrib gives rise to two of the xylem poles 
of the root, while the third, as well as the two remaining phloem groups, are 
supplied partly by it and partly by the chief bundle of the dropper (Fig. 9 d). 
The latter is a double bundle with a single xylem group and two phloems, 
and occupies the position in the dropper corresponding to that of the mid- 
rib in the leaf. There are six bundles in the transverse section of the 
dropper (Fig. 9 e) : the midrib which connects with the root, the two 
laterals which are continuous with the laterals of the cotyledon, the small 
inverted bundle which also continues right into the cotyledon, and one 
bundle on each side arising as a branch of the cotyledon midrib. By the 
outward migration of the small inverted bundle a ring of bundles is formed 
in the dropper in place of the comparatively leaf-like arrangement in the 
cotyledon. The second seedling which I cut differed from this one in 
the absence of the small inverted bundle. 
1 Asa Gray, A New Species of Erythronium , Amer. Nat., 1871, p. 298. 
2 F. H. Blodgett, Vegetative Reproduction and Multiplication in Erythronium, Bull. Torrey 
Bot. Club, xxvii, p. 305. 
3 E. Sargant, loc, cit. 
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