44 



EXPERIMENTS IN BLUEBERRY CULTURE. 



as occurs on the roots of oaks. In the latter type of mycorrhiza the 

 hypha^ of the fungus form a dense sheath around the rootlet, com- 

 pletely shutting it off from direct contact with the surrounding soil. 

 The loose hypha' on the outside of the sheath resemble root hairs 

 and it is supposed to be a part of their function to absorb soil mois- 

 ture and transmit it to the oak rootlet just as root hairs do. 



It has not yet been possible, for want of time, to study the life 

 history of this mycorrhizal fungus of the blueberry. There is, how- 

 ever, a clew to its identity in the work 

 of Miss Charlotte Ternetz, Ph. T)., 

 described on page 49. 



The experiments thus far made do 

 not warrant a supposition that any 

 good peat soil requires inoculation 

 with the mycorrhizal fungus before 

 blueberry plants will grow well in it. 

 The fungus appears either to be al- 

 ready in the soil or to accompany the 

 seeds when they are soayu in it. 



(15) The mycorrhizal fungus of the 

 swamp blueberry appears to have 

 no in.)urious effect, but rather a 

 beneficial effect, upon the blue- 

 berry plant. 



The epidermal cells in which the 

 mycorrhizal fungus occurs are not 

 swollen nor distorted, nor do their 

 contents collapse or show any of the 

 other effects usually produced by 

 pathological fungi. They appear to 

 differ in no respect from other epi- 

 dermal ceHs of the blueberry rootlets, 

 hyphse of the mycorrhizal fungus; j^^ rai)idlv prowing rootlets the fun- 



c, internal hyphje ; d, point of pene- ^ ■ '^^ i i i i. i 



tratiou of the cell wall by the gus scems uot to be able to Keep pace 



mycorrhizal fungus. (Enlarged ^^,-^|^ ^^^^ rootlet itself and mav not 

 about 1,000 diameters.) . ^ , , -,. ^ ' , , 



occur for a considerable distance back 

 from the growing tip. The fungus-filled cells ordinarily are most 

 numerous on certain small, short, and crooked lateral rootlets the 

 growth of which is slow. When root growth of a vigorous plant is 

 retarded or becomes even stagnated, the fungus may invade the epi- 

 dermal cells to the very apex. Sometimes half the cells in such a 

 rootlet are gorged with fungi, yet the delicate cell walls show no 

 displacement or distortion. There is no indication whatever that 

 the fungus causes any pathological disturbance or is in any way 

 obnoxious to the plant. On the contrary, the uniformity with 



193 



Fig. is. — -Mycorrhizal fungus of Knl- 

 mia latifolia in an epidermal cell of 

 the root : a, Cell walls ; h, external 



