SOME FEATURES OF OAK GALL GROWTH. 15 



attain 30 mm. in length and 12 mm. in girth. A. 

 seminationh (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 leno'th. 



Texture .- (c) Succulent. — There is little difference 

 in the soft and juicy nature of SpatJtega.ster haccarum 

 and Trigonaspis crustalis. A gall of either species 

 measuring 42 mm. in girth contains 12- J 4 minims of 

 fluid. A specimen of Dri/ophanta scidellaris will yield 

 a large amount of fluid, but not so much in proportion 

 to the gall-substance as the former species. From 

 Aphilotliviv radicis and Teraa tenninalis a moderate 

 amount of moisture can be expressed. No other gall 

 contains a sufficiency of moisture worthy of remark. 



(d) Woorlij. — This term, of course, applies only to 

 galls when mature. All are more or less soft during 

 the early stages of formation. Of simi3le structures, 

 those of Andricus curvator on twigs and petioles, 

 A. inflator, and A. solitariu>i are moderately woody. 

 Others of a harder texture are ApJiilofhrix corticis, 

 A. Sieholdi, Biorlika altera, and those of the Dryo- 

 phanta genus. The small hard cells of Andricus 

 ramuli, and the conglomerated cells wdth the sur- 

 rounding woody growth of Aphilothrix radicis are, 

 however, surpassed by G. Kollarl, which is the hardest 

 and most woody of all. 



Colour : (e) Green. — Green is the prevailing colour. 

 It is due entirely to chlorophyll. From an exceed- 

 ingly pale shade, as in Sijatliefjaster 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. 



