Robertson — The ‘ Droppers' of Tulip a and Erythronium. 433 
and emerged from the top of the bulb side by side with the foliage leaf to 
which it belonged. Its tip, which was coiled like a ram’s horn, contained 
the usual small bulb, and, in addition, there was a second one growing outside. 
Since the dropper is neither purely axial nor purely foliar the question 
arises as to whether its region of greatest growth will be at the base as in 
leaves, or immediately behind the apex as in roots. To decide this, two 
bulbs of T. sylvestris were grown as water-cultures, and when they had 
each produced a dropper f inch long, the foliage leaf and dropper in one 
case were divided with lines of Indian ink into zones of -J inch, and in 
the other into zones of \ inch. After a few days it was found that in 
each the growth of the leaf was much greater in the lowest zone, and that 
of the dropper in the zone next behind the apex. So the growth of the 
dropper resembles that of the root. 
I have examined the vascular transition from leaf to stem and dropper 
by means of serial sections (cf. Figs. 4 e , f g, h y and Fig. 5 b) } and 
also by placing the whole transition region in concentrated carbolic acid 
kept at a temperature just above its solidifying point. This produces 
sufficient transparency to allow the veins to be followed under the dissecting 
microscope. Fig. 2 e and Figs. 6 /, g, h y were drawn from such pre- 
parations. In T. saxatilis and T. sylvestris both these methods have been 
used for comparison, but in T. praecox the carbolic method only, and in 
T. Clusiana sections only have been employed. The anatomy is essentially 
the same in all four species. In general terms we may say that the 
bundles on the side of the cylindrical leaf base remote from the midrib run 
straight down to form the vascular system of the corresponding abaxial 
side of the dropper. The midrib and main laterals on the other hand run 
directly down into the stem rudiment, but each before entering it gives off 
a branch to supply the adaxial side of the dropper. These two sets of 
foliar bundles form a complete ring round the dropper. Complications are 
sometimes introduced by bundles starting from the stem rudiment which 
run a little way up into the leaf and then suddenly dive down into the 
dropper, or dip down into the dropper and then rise at a sharp angle into 
the leaf. The midrib and the main laterals of the leaf enter the dwarf stem 
in a crescent, but soon arrange themselves in a circle. From the side of 
this towards the dropper, two or more bundles as a rule send branches into 
the dropper, which course down its adaxial side outside the foliar vascular 
ring. The orientation of the bundles on the adaxial side of the dropper is 
very variable. The foliar bundles are inclined to place themselves so as 
to form, with the axial bundles, a more or less complete ring. In the 
dwarf stem the bundles, as we pass downwards, become concentric by the 
creeping of the xylem round the phloem and then fuse into an irregular 
plexus, which ultimately divides up completely to form the vascular 
systems of a crop of 3- to 5-arch adventitious roots (Fig. 5 b). 
