Mite-induced Galls of Hoheria s exstylo sa — Arnold 
503 
Fig. 1. A large actively growing mite gall. 
In all the above experiments plastic bags 
were kept over the treated plants for a week. 
After two years no galls had appeared on 
any of the plants. It remains to repeat these ex- 
periments at other seasons of the year. 
OBSERVATIONS 
The opening of flower buds of Hoheria sex- 
stylosa in late summer marks the recrudescence 
of gall formation. Some infested buds show 
traces of stunted petals and stamens, but often 
only the calyx and pedicel remain unchanged, 
and a mass of convoluted greyish-green tissue 
takes possession of the interior region. It is the 
persistence of the pedicel and calyx which gives 
to young galls their top-shaped appearance 
(Fig. 2). 
A small percentage of unfolding young leaves 
may develop galls at this time. The distortion 
may be considerable and the leaf blade may 
be almost lacking. In other cases leaf develop- 
ment may not be greatly Impeded and the galls 
may be relatively insignificant. 
On some trees hardly one in a thousand 
flower buds escapes attack, so that by autumn 
the plant is festooned with the new growth of 
galls and it is difficult to find one seed head 
on the whole tree. 
Sections through living galls show them to 
consist chiefly of a solid mass of green paren- 
chyma Interspersed by clear mucilaginous cells. 
Within the parenchymatous cells crystals of 
the druse type are not infrequently encoun- 
tered. The cavities beneath the surface in whrh 
mites can be seen moving are lined by a defi- 
nite grey merlstematic layer. The exterior of 
the gall is bounded by a well-marked and active 
periderm. 
In older galls the core of the gall is white, 
being made up of abundant vascular tissues and 
non-chlorophyllous parenchyma. This massive 
development of vascular tissues Is readily dem- 
onstrated by allowing a gall to decompose for 
a week in tap water. Disintegration of the soft 
tissues reveals a compact mass of xylem. radi- 
Fig. 2. Flowering twig of Hoheria sexstylosa Col., 
showing some flower buds recently transformed into 
galls, and one older gall at base. 
