INJURIES INDUCED BY PLANTS 



may be taken for granted that the products of solution are absorbed 

 by the cortex-roots and used for their own growth. From investi- 

 gations made on the Scotch pine and the silver fir, the annual 

 growth in length of the cortex-roots is 75 mm. in the former case 

 and 1 75 cm. in the latter. The growth in thickness would appear 

 to be somewhat irregular. Once a 

 year, very seldom twice, often only 

 each alternate year, a " sinker " 

 originates on the inner side of the 

 cortex-root near the apex. This 

 wedge-like outgrowth is of the 

 same breadth as the cortex-root, 

 but varies much in thickness, and 

 breaks through the cambium zone 

 until it just reaches the wood of 

 the host-plant, where it elongates 

 in the same peculiar manner as 

 has been already described in the 

 case of the radicle. If the cortex- 

 root with its sinkers is exposed, as 

 is represented in Fig. 2, we may 

 trace back from the apex of the 

 root c, and accurately determine 

 how many years have elapsed since 

 the various sinkers have originated, 

 because each year these are em- FJG . 2 ._ R oots of Viscum album 



braced by a wood-ring. Even in 

 the most recent descriptions of 

 the mistletoe we still find, as a 

 rule, Schacht's illustration repro- 

 duced, which erroneously represents 

 young sinkers between older ones 

 on the same cortex-root. Water 



in Pinus sylvestris. The cortex- 

 root, which pushes its apex, c, 

 along the bast tissues, , puts 

 forth eight sinkers on the inner 

 surface, and buds and shoots on 

 the outer. The oldest portion 

 has already been pushed out 

 nearly to the dead bark. At e 

 the sinkers of a cortex-root which 

 has already been enveloped in 

 the bark are shown. 



and inorganic nourishment are 



absorbed by the whole series of sinkers through their lateral 

 surfaces, which are in immediate contact with the water-con- 

 ducting organs of the wood, and are first of all conveyed to 

 the cortex-root, and through it to the leafy part of the mistletoe. 

 From the peculiar way in which the sinkers increase in length 



