28 BORTHWICK—ADVENTITIOUS ROOTS AND RELATION 
general impression presented by a portion of one of those trees 
In Plate X., Fig. 37, we have a detached branch with its spur- 
shoots ; at the base of each spur-shoot a number of those conical 
projections may be seen, while at the base of the branch itself 
their massed arrangement is very apparent. Plate X., Fig. 36, 
is the basal portion of Plate X., Fig. 37, enlarged. 
It may be well to mention here that these outgrowths were 
evidently in no case the result of previous wounds and had not 
been preceded by any callus formation. 
In order to see how they would behave when brought into 
heat and moisture, a cutting was taken from one of the trees and 
placed in a forcing frame of a warm moist glass-house. The 
conical protuberances in a surprisingly short time (36 hours) had 
elongated about 6mm. and in two days were 13mm. in length. 
This specimen is shown in Plate X., Fig. 35. When put into 
moisture and heat the protuberances were in the same condition 
as those seen in Plate X., Fig. 37. It will be observed that in 
their growth the roots have a downward tendency. This is well 
seen in Plate X., Fig. 34, which is a photograph of a cutting 
laid horizontally on the fibre of the forcing frame in the hot- 
house. The roots then grew vertically downwards into the fibre. 
Moisture, as might be expected, has a great effect on the rate 
and direction of their growth. 
Plate XI., Figs. 39, 40, and 41, illustrate the effect of causing 
one of the roots to grow into a glass tube filled with sand. Fig. 
39 shows the cutting before the tube was attached. Fig. 4! 
indicates how the tube was attached ; the root is seen growing 
into it; while in Fig. 40 we have the root after the tube was 
removed. That those structures have a strong geotropic tend- 
ency is clearly shown in Plate X., Figs. 32 and 33. A cutting 
was inverted so that its apex pointed in a downward direction ; 
when the roots developed, their direction of growth was towards 
the turned-down apex, Plate X., Fig. 33. After being allowed 
to remain in this position till the roots were about 6mm., the 
cutting was re-inverted, so that base and apex each occupied its 
normal relative position; this was immediately followed by a 
downward curving of the root-tips (Plate X., Fig. 32.) 
When the air-moisture was sufficiently great, a fine felty 
covering of white silvery hairs was developed. The sard- 
