30 ART. 10. S. IvUSANO : STUDIES ON THE PARASITISM 



was before stated, firmly to the cortex of the host, compressing 

 and deforming the tissue of the latter between the sucker and 

 themselves (Fig. 7). 



The cortical tissue of the host, however, continues, during 

 the secondary growth, to die away gradually from the outside 

 and becomes replaced by its new layers formed from the cambium ; 

 and when the outermost decayed tissue of the cortex comes to 

 be cast away, the folds, which were formerly in contact with it, 

 detach naturally from the surface of the host, imitating a roof 

 projecting laterally on the lateral side of the haustorium, as will 

 be seen in the advanced stage of Fig. 10 (at). While the fold 

 is thus gradually removed from the host, another change occurs 

 which causes the disappearance of the fold. 



Generally towards the end of the primary growth, the forma- 

 tion of the corky layer is observed under the superficial par- 

 enchyma of the fold, and those cells lying outside this corky 

 layer will ultimately detach from the fold and be cast off. As 

 the age advances, therefore, the folds are no longer sharply edged 

 as before and form only rounded elevations. 



At last after the successive formation of the corky layer, the 

 folds disappear entirely, so that the surface of the haustorium 

 becomes homogeneous throughout (Fig. 21). 



While the modification of the structure is thus going on in 

 the frontal portion of the cortex, the shape of the central part 

 at the apex of the haustorium will gradually deviate from that 

 which it had at first. Now the frontal part of the haustorium, 

 when young, is distinctly divided into the peripheral and the 

 central portion, which are respectively the attaching-folds and 

 the sucker ; the latter however being simply imbedded in the 

 tissue, especially in the cortex, of the host shows no difference 



