SOME FEATURES OF OAK GALL GROWTH. 15 
attain 80 mm. in length and 12 mm. in girth. 4. 
seiminatiouis (thought by some writers to be the same 
gall), which develops on the catkin instead of on a 
twig,is the next in length, but it seldom exceeds 8 mm. 
in length. 
Texture: (c) Succulent—There is little difference 
in the soft and juicy nature of Spathegaster baccarum 
and Prigonaspis crustalis. A gall of either species 
measuring 42 mm. in girth contains 12-14 minims of 
fluid. A specimen of Dryophanta scutellaris will yield 
a large amount of fluid, but not so much in proportion 
to the gall-substance as the former species. From 
Aphilothriv radicis and Teras terminalis a moderate 
amount of moisture can be expressed. No other gall 
contains a sufficiency of moisture worthy of remark. 
(d) Woody.—This term, of course, applies only to 
galls when mature. All are more or less soft during 
the early stages of formation. Of simple structures, 
those of Andricus curvator on twigs and _ petioles, 
A. injlator, and A. solitarius are moderately woody. 
Others of a harder texture are Aphilothriv corticis, 
A. Sieboldi, Biorhiza aptera, and those of the Dryo- 
phanta genus. The small hard cells of Andricus 
vamuli, and the conglomerated cells with the sur- 
rounding woody growth of Aphilothria radicis are, 
however, surpassed by C. Kollari, which is the hardest 
and most woody of all. 
Couour: (e) Green.—Green is the prevailing colour. 
It is due entirely to chlorophyll. From an exceed- 
ingly pale shade, as in Spathegaster tricolor (denuded of 
hairlets), or Aphilothrix corticis, various gradations of 
this colour are to be found until as deep a shade as 
seen in any oak twig or leaf is manifested in many 
specimens. The most beautiful of all green shades is, 
perhaps, that of the oak-marble, when in June and 
July its epidermis is a beautiful golden green. Green 
is generally succeeded by brown of various shades. 
The brown pigment is probably due to tannin taking 
the place of the chlorophyll. 
