Clifford : The Mvcoriiiza of Tipularia unifolia 637 



that this may be a true many-layered epidermis, developed for the 

 especial needs of a mycorhizal or^^an, similar to that described by 

 Groom in TJiisuiia (Annals of Botany, 1895), The outer wall of 

 the external layer is extended in the form of root-hairs which are 

 persistent, and which exhibit great div^ersity of shapes. Some of 

 these organs are branched, while the apices of others are converted 

 into hollow disks, or into tlie form of the pileus of a mushroom. 

 These hairs are traversed by hyphae which pass through their 

 lateral walls into the humous soil. 



The cells of the epidermal tissue contain hyphae which pass 

 towards the apex of the root in nearly straight lines. The hyphae 

 give off short lateral branches which are enlarged, and are of the 

 form of the sporophores of some of the moulds, though never seen 

 to develop spores. These organs are cut off from the main hyphae 

 by septae, and are sometimes to be seen separated from the hyphae, 

 and may possibly serve as reproductiv^e bodies. The hyphae are 

 septate throughout all of the regions mentioned. 



The hyphae which traverse the root-hairs sometimes form con- 

 volutions within them, and nearly all of the hairs thus inhabited 



I 



show distortions as previously described. 



In addition to the symbiotic fungus, the smaller hyphae of a 

 second organism, probably parasitic may be seen in the roots of 



some specimens 



Summary 



The principal features of 



Tip 



laria consist in the lack of the root cap, the development of a 

 many-layered epidermal tissue, which serves the immediate pur- 

 pose of affording a habitat for the vegetative mycelium of the sym- 

 biotic fungus : the formation of a special sheath from the ex- 

 ternal layer of the cortex, certain cells of which are converted 

 into passage-cells, through which the internal hyphae find an easy 

 passage into the medio-cortex with its rich content of carbohy- 



drates. 



The general organization of the fungus, and its relation to the 



seed plant is similar to that described by MacDougal in Corallo- 



rhiza and other mycorhizal forms.* The hyphae in the epidermal 



* Symbiosis and Saprophytism, Bull. Torr. Bot. Club, Oct., 1899. 



