282 



DEFINITE ACTION OF THE 



Chap. XXIII. 



service to the two series in the Old and New Worlds ; there- 

 fore these peculiarities cannot have been naturally selected. 

 Hence we are led to infer that they have been definitely caused 

 by the long-continued action of the different climate of the two 

 continents on the trees. 



Galls. — Another class of facts, not 



relating 



to 



iltivated 



plants, deser 



I allude to the production of g 



Every one knows the curious, bright-red, hairy productions on 

 the wild rose-tree, and the various different galls produced 



by the oak 



osy 



as 



Some of the latter resemble fruit, with one face 

 •osiest apple. These bright colours can be of 



as 



service either to the gall-forming insect or to the 

 probably are the direct result of the action of the li 



and 



same ma.nner as 



the 



pples of Nova Scotia or Canada are 

 brighter coloured than English apples. The strongest upholder 

 of the doctrine that organic beings are created beautiful to please 

 mankind would not, I presume, extend this view to galls. Ac- 

 ding to Osten Sacken's latest revision, no less than fifty-eight 



■ ■ 



kinds of galls are produced on the several species of oak, by Cynips 



with its sub 



& 



and Mr. B. D. Walsh 47 states that he 



add many others to the list. One American species of willow, 

 the Salix humilis, bears ten distinct kinds of galls. The leaves 

 which spring from the galls of various English willows differ 



completely in shape from the natural 



The young shoot 



of junipers and firs, when punctured by certain insects, yield 

 monstrous growths like flowers and cones; 



some plants become from the same 

 appearance. 



and the flowers 

 wholly changed 



mce. Galls are produced in every quarter of tl 

 of several sent to me by Mr. Thwaites from Ceylon, som 

 symmetrical as a composite flower when in bud, other 



as 



smooth 



and spherical like a berry ; 



protected by 



long 



spines 



> 



others clothed with yellow wool formed of long cellular 



gularly tufted 



3, but in 



In some gall 



structure is sim 



M. Lucaze-Duthiers 48 has figured 



less than seven 



it is highly complex; thus 



in 



the 



•g 



lay 



4 ? See Mr. B. D. Walsh's excellent 



us, composed of distinct tissue, 



48 See his admirable Histoire des 

 papers in ' Proc. Entomolog. Soc. Phila- Galles, in ' Annal. des Sc. Nat. Bot.,' 

 delphia,' Dec. 1866, p. 284. With respect 3rd series, torn, xix., 1853, p. 273. 

 to the willow, see idem, 1864, p. 546. 



