FUNGOUS ROOT-TUBERCLES. 83 



The tubercles originate from the small adventitious roots 

 which do not attain more than several centimeters in length 

 when infection takes place. Many roothairs occur on these 

 roots, and it is quite probable that the fungus, in some form, 

 makes its inroad through them or by some epidermal cell of 

 the growing root. The formation o 



mass 



where probably 



material 



m 



for investigation was taken from 



and 



tures. 



>ns, of which Kaiser's sublimate-acetic and Fleming s 

 r fluid proved to be the better fixative for these struc- 

 After fixation, the ordinary procedure of dehydrating, 

 hardening and imbedding was followed, though a much 

 longer time was given for infiltration than is usually given 

 for tissues of a softer texture. Tangential, median and trans- 

 verse sections 5 to 6fi in thickness were made and stained 

 with Fleming's triple and Heidenhain's iron haematoxylin. 

 The haematoxylin stains the nuclear structures of the fun- 

 gus, but the mycelial wall and different parts of the host cell 

 can be made out with difficulty. Most of the drawings were 

 made from sections prepared only with the triple I 



may best 



from 



tubercle 



rmis which is usually broken 



gular except in very young forms. Underneath lies 



made 



ihymatous cells. The outer portion of this contains narrow 



thickness, 

 isodiametric 



measuring 



make up a layer from 4 

 >f this there is a layer of cells almost 

 ery thin walls. Farther toward the in- 

 line larger and radially elongated, some 

 y 28 to 45*t. These cells contain the 



forming 



layers in thickness. 



region 



smaller cells mostly isodiametric with a few 



gularly amongst them 



bounded by an endodermis com- 

 posed of small oval thick-walled cells which stain quite 



