CANKER. 467 



inspection, however, the difference is only apparent ; 

 for even the smooth twigs have decayed spots, 

 involving the superior organs. 



" If the cankered branch be examined as soon as 

 the mischief is visible, a vertical section through 

 the pith generally reveals the point at which decay 

 has commenced ; some bud, frequently a fruit-bud. 

 The flowers, in the first instance, may not have set, 

 on account of some one of the causes which usually 

 produce sterility. The foot-stalks may have sep- 

 arated from their point of attachment, leaving the 

 bud in a state unfit for further vegetation. The 

 young fruit may still remain withering on its matrix, 

 which has not vitality enough to throw it ofi'. Either 

 the matrix itself or the dry fruit decomposes as the 

 season advances. The morbid matter is carried 

 down to the tissues surrounding the pith. If the 

 branch has strength enough to resist the infecting 

 matter, the wound is soon covered over with fresh 

 layers of wood, and no permanent injury results. 

 On the contrary, if the constitution be weak, and 

 the vitality low, the woody tissue perishes, and soon 

 involves the bark which covers it, so that both are 

 incapable of transmitting the nutritive fluids, and it 

 perishes as if by a flash of lightning. 



" Where there is great weakness of constitution, 

 it is obviously very difiicult to contend against the 

 disease. Something may be done by very careful 

 inspection of the trees, and by the removal of every 

 unhealthy sjDur" (Berkeley). 



