34 ART. 10. S. K USA NO : STUDIES ON THE PARASITISM 



longest neck I have ever seen. During the secondary growth, 

 however, the axial part is the most important factor in deter- 

 mining the outer form of the haustorium, for, as it was before 

 explained, this part is the most changeable in form, so that the 

 form of the haustorium mainly accords with that of the axial 

 part. When the axial part becomes rounded in cross-section, the 

 outline of the haustorium is also rounded ; and when in the old 

 haustorium the axial part becomes again elliptical, the surface 

 view of the haustorium is also elliptical. The chief modification 

 of the cortical part is then that the attaching-fold obliterates, 

 leaving in a certain stage concentric furrows along the front of 

 the haustoria, which however disappear in very old specimens. 

 That the old haustorium does not increase at all in its height 

 and thus becomes flat, has already been briefly stated. 



VI. GENERAL REMARKS AND SUMMARY. 



It would be of much interest to inquire how far the above 

 described structure of the haustorium of Buckleya resembles that 

 of the same organ in the allied species, and to what extent 

 my interpretations concerning the nature of its tissue can be 

 applied to others ; but, as to the latter point, I can refer only to 

 a few species, since in many parasitic Santalaceœ the structure of 

 the haustorium has not yet been studied. In Thesium, Santalum, 

 Osyris and Buckleya the structure of the haustoria is the same 

 in general respects ; thus we find in all of them the cortical 

 and axial part, 1 ' including the sucker, attaching-fold and striated 



1). The part called by me the axial part docs not correspond to the "Kern" defined by 

 other authors in other species, for they included in "Kern" the cambium as well as 

 parenchyma, which latter must lie properly included in the cortical part according to my 

 désigna dun above given. 



