638 Clifford: The Mycorhiza of Tipularia unifolia 



tissue constitute the vegetative mycelium, which sometimes forms 

 branches which may be reproductive in their primary purpose. 

 Branches are given off which traverse the root-hairs and pene- 

 trate the soil, constituting the absorbing organ of the mycorhiza, 

 and which serve to bring the humous products within the root. 

 Branches are given off which penetrate the cortex through the 

 passage cells, forming vesicles which serve as organs of inter- 

 change. Starches and other carbohydrates are taken from the 

 higher plant, and proteids are formed from these and the humous 

 products brought in from the soil, which are finally liberated by 

 the disintegration of the vesicles. The seed plant affords a 

 habitat also to the fungus, so that a fairly well balanced symbiosis 

 Is the result. 



explanation of Plate 372 



■ 



All drawings were made from a Baiiscli and Lomb one-fifth inch apochromatic ob- 

 jcclive, and a No. 4 compensating ocular. Magnification 159 except in figure. 



Fig. I. Cross section of stele, x, x, x, x, x, scalariform ducts, j, spiral vessels. 



Figs. 2 and 3. Root-hairs, showing form and traversing hyphae. 



Fig. 4. Tangential view of outer cortical sheath, showing the long cylindrical 

 sheath cells, alternating with the short passage-cells. 



Fig. 5. Longitudinal section of cortex and epidermis, r, outer epidermal cells 

 with root-hairs, s, sheath, o, region containing vegetative mycelium of fungus, w, 

 medio-cortex. //, disintegrating vesicles. ;;, nucleus. 



