120 WOODY PLANTS OF MASSACHUSETTS. 



side of the branch a spherical gall of one-fifth to one-quarter of 

 an inch in diameter. These are found single, or two or three 

 together, near the extremities of the smaller branches. If cut 

 open in winter, they expose a worm or chrysalis folded up 

 within a bony case. 



For an account of the modes that have been devised to pre- 

 vent or remedy the mischief done by so many enemies, I must 

 refer to the Report of Dr. Harris, to whom I am indebted for 

 almost the whole of what I have given above, and who has 

 done more than all other persons in the investigation of the 

 difficult subject of the habits and ravages of the insects of Massa- 

 chusetts ; more, indeed, by original observation, than has ever 

 before been done, by any person, in any country or State what- 

 ever. Care and precaution may do something; but against 

 many of these insects the unassisted efforts of men can accom- 

 plish very little. Most of the birds, probably all of them, the 

 smaller quadrupeds, and all the reptiles come to our aid and 

 wage perpetual war upon the insect tribes. The woodpeckers 

 and the creepers do what they can to keep the bark of trees free ; 

 the fly -catchers take care of the leaves ; a single flock of wild 

 pigeons will do more than an army of foresters against the large 

 solitary caterpillars which infest the oak forests. 



The bark of most species of oak contain the tannin princi- 

 ple. The cups of the Velani oak are used for dyeing and for 

 tanning. Both purposes are effected by the bark of our com- 

 mon black or yellow bark oak. The bark of a species of oak 

 which grows in Spain, Quercus subcr, furnishes the invaluable 

 substance, cork, which is used in the countries where it is 

 produced, not only for the purposes to which we apply it, but 

 also as a lining and a carpet in brick or stone habitations. 



The bark of most of our oaks is useful to the tanner, particu- 

 larly that of the white oak, the chestnut oaks, and others of the 

 same group. 



Yet the great value of the oak. in all countries, is for its wood. 

 It is applied to a greater variety of important purposes than 

 that of any other tree. With the exception of the teak tree, it 

 forms the best ship timber known ; and, for this purpose, the 

 white oak is, perhaps, equal to the English oak, and surpassed 



