196 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 
met with. Its stem is creamy white in colour, and furnished 
with scale-like bracts, and dull, purplish, drooping flowers. Its 
underground portion bears white succulent fleshy scales, closely 
packed together, and its roots are fused with those of the host- 
plant, at the base of which it is found. There are no green 
leaves on the aerial portion of the stem, as such are dispensed 
with by a parasite, whose growth is not dependent on a supply 
of light, and this explains why the toothwort may be found 
growing in dense shade at the base of beech trees, even in 
a close wood. It cannot, however, be called a destructive 
parasite. 
2. Report by R. Stewart MacDoueca.t, M.A., D.Sc., F.R.S.E., 
Honorary Consulting Entomologist. 
THE Oak TorTRIX OR LEAF-ROLLER. 
Tortrix viridana, Linn. 
This pretty but destructive enemy of the oak belongs to the 
family Zortricide, a family of small moths that have a large 
wing-spread. The caterpillars live variously, according to the 
species, in rolled-up leaves, or internally in young stem or fruit. 
The word Zortrix refers to the habit that some species of the 
caterpillars have of rolling or twisting up leaves. The manner 
in which the caterpillar manages to roll up the leaf has attracted 
the attention of various observers, and, as Dr Sharp points out, 
has been ascribed to “the immediate operations of the larve, 
to the contraction of the silk threads when drying, and to 
changes in the mode of growth of the attacked organ, due to 
the interference of the caterpillar.” 
Certainly the rolled-up leaf affords advantages to the cater- 
pillar, which feeds under protection on the rolls, the excrement 
escaping by one of the open ends of the roll. Such excrement, 
in the case of severe attack by the oak leaf-roller caterpillar, 
may be found strewing the ground, and is a means of calling 
attention to the attack. 
The genus Zortrix is a very large one, and has a very wide 
distribution. Our insect, Zortrix viridana, is found in Great 
Britain and Ireland, over the whole of Middle Europe, east into 
Russia, and south into Italy. More an insect of level tracts, it 
is yet found at considerable heights above the sea-level. 
