no 



THE FACTORS 



[Part 



however forms, as soon as it comes into contact with the nucleus, a vesicle that i 

 egg-shaped or pear-shaped and becomes filled with cytoplasm and nuclei (Fig. 60 

 After a time the contents of the vesicle become disorganized and transformed int 

 a yellow, granular mass. The nucleus in the meantime has changed its position i 

 the cell, but the terminal point of the mycelial thread follows it, and, in contact witl 

 it, repeatedly forms fresh vesicles. In the outer region of the cortex the hyphae liv 

 longer and exhibit less connexion with the nucleus or (in the sheath) none at al 

 Groom attributes, without doubt correctly, the growth of the terminal point of th 



Fig. flS. Fagussylvatica. Mycorhiza with 

 fungal hyphae. Magnified 9.' After Ka- 

 mienski. 



Fig. 59. Thismia Aseroe. Cortex of tlie myo 

 rhiza. After P. Gi 00m. 



hyphae in the direction of the nucleus, to chemotropism. The same thing occui 

 in the case of undoubtedly parasitic fungi, for instance in Puccinia asarina ar 

 Hemileia vastatrix, the fungus of the coffee disease, and is quite general in endi 

 trophic mycorhiza. It is clearly due to a product near the nucleus arising chiefly in tl 

 inner cortical layers. The swelling is due to vigorous nutrition, for a similar phen 

 nienon also occurs in cultures of fungi in nutritive solutions, if the concentratic 

 of the latter be increased. That the solution of the starch is to be associated with tl 

 formation of proteids in the vesicles is obvious from what has been said before. 



