Osborn.— Some Observations on the Tuber of Phyltoglossum . 501 
experiment lasted, all the leaves early began to curl upwards, becoming J- 
or U-shaped as one or both ends were elevated. 
The curling was not due to the effect of light, for frequently the 
proximal end was elevated, whilst the apex showed no response. It was 
noticed that in dry weather the leaves of plants growing in the field might 
show a marked incurving of their tips. It therefore appeared probable that 
the curving was due to some alteration in the turgidity of the leaf. This 
point is further discussed later (p. 510). 
By August 31 all the leaves* showed more or less adventitious growth 
near the proximal end. Most of the cell masses were lifted above the soil 
owing to the curvature of the leaf. All of them had an irregular contour. 
The appearance about this date is shown in Text-figs. 31 and 32 A, drawn 
September 16. As it was feared that the cell masses might dry up because 
of the elevation of the proximal ends, some of the leaves were laid flat upon 
the soil. On October 21 the leaf shown in Text-fig. 32 A was sketched 
again (Text-fig. 32 B). It will be seen that the cell mass now showed 
distinct scattered nodules. These were green, no white growing-point 
being seen. 
By the middle of November it was necessary to stop the experiment. 
Only one leaf (Text-fig. 30), that which lay horizontally, showed a single 
tuber resembling those formed in the other series. Text-fig. 32 C shows 
the condition of the leaf drawn in Text-figs. 32 A and B. The nodular 
growths noticed before had most of them elongated to form minute stalks 
terminating in slightly swollen- white heads. Text-fig. 33 A shows another 
leaf viewed from above. The cell mass is seen to be near the proximal 
end, but on the convex side of the curved leaf. Stalklets bearing small 
white heads are visible. Viewed from the side (Text-fig. 33 b) it is seen 
that these minute tuber structures, developed irregularly over the cell mass, 
are markedly geotropic in their growth, though several of the stalks were 
not sufficiently elongated to bury their apices. The leaf shown in Text- 
fig. 34 A (also drawn from above) had its apex erect. From the under 
surface of this (Text-fig. 34 B) many irregular white nodular structures of 
various sizes were developed. 
The leaf shown in Text-fig. 35 is interesting. In this case the 
adventitious cell masses were scattered over a greater length of leaf 
than is usual. The majority of them merely developed short stalks in the 
white swollen heads. Two of the growths, however, developed leaflets as 
well as descending portions. By November 17 the original leaf was 
obviously dying off, so that it was necessary to fix it, and further develop- 
ment could not be followed. It will be noticed, however, that each leaflet- 
bearing structure resembles that shown in Text- fig. 20 A, but at an earlier 
stage. 
O o 
