dOO STUDIES IN SYMBIOSIS. 1., 



In a longitudinal section of the root apex it is seen tliat the sheath passes 

 over the tip (Text-flg. 7). None of the cells of the sheath are developed like 

 root-hairs as is common in some forms of saprophyte (e.g., Thismia). The cells 

 of this sheath arise from the primordial meristem cells at the apex; the exo- 

 dermis, cortex and central cylinder all merge imperceptibly into the primordium, 

 the cells of which are very small and nnmerous. Kaphide cells occur almost to 

 this meristematic zone, but the endophytic fungus does not approach its vicinity. 

 The infected cells occur in the zone of differentiation where the tissues have 

 assumed their final form. Fungal hyphae do not enter the meristematic zone, 



Text-fig. 7. — A longitudinal section of the rfyot apex showing the 

 meristems, and the fact that the endophyte does not 

 'develop near the meristematic zone (x 1.5). 



nor do they cause any hypertrophy of the host-tissues. All the tissues of the 

 host are directly traceable to the primordial meristem which is uninfected by 

 the fung-us. 



The fungus occurs in the soil surrounding the root in the form of numerous 

 branching, fine hyphae, many of which form a close tangle on the surface of the 

 root from which hyphae pass inwards through the sheath and outwards into the 

 humus. I have observed numerous cases of the hyphae in the sheath-cells; 

 generally only one hypha occurs in a cell, but I have seen two or three cases 

 where more than one hypha was present. The hyphae pass straight towards 

 the endodermis. Many may continue their course directly into the cortex through 

 a passage-cell, but it sometimes happens that the hyphae have to pass obliquely 

 through the inner cells of the sheath to reach the passage-cells. Branching of 

 the hyphae occurs in the cells of the cortex immediately within the passage-cells ; 

 very occasionally in the passage-cell itself. I have observed the connection of 



