1915] HARVEY & ROSE—ILLUMINATING GAS 
Ww 
~~] 
is brought about through an increase in size of the cortical cells, 
and particularly by rapid proliferation at the phellogen layer. 
d) Ailanthus seedlings; 
illuminating gas; exposure 
period 15 days; concen- 
trations 1:400, 1:10, and 
controls. 
1:400 gave slight swell- 
ing in tap root near the 
surface of the soil; while 
in the 1:10 the leaves 
began falling after 5 days, 
and had all fallen before 
the end of the exposure. 
The tap roots were much 
swollen for 3-4 cm. below 
the surface of the soil. 
e) Same as (d) but with 
ethylene instead of illumi- 
nating gas; concentrations 
1:10,000 and 1:250. 
Swollen zone of tap 
root was somewhat more 
pronounced in the 1: 10,000 
than in the 1:400 illumi- 
nating gas above. In the 
1:250 all plants had lost 
their leaves within 8 days, 
and the tap roots were 
much swollen. The mor- 
phological nature of these 
swellings may be seen in 
figs. 5 and 6. In fig. 6 ae Sindee 
. 5 chested “with illuminating gé 
are two outlines of trans- 
verse sections of the tap roots of Adlanthus seedlings in the region 
where swellings take place; A, the control plant; B, a treated plant. 
Fig. 5 shows the detailed structures of the regions outlined in A 
_ controls; B, 
go 
So 
