516 MacDouoal : Symbiosis and Saprophvtism 



species was a true saprophyte (ii). Recently, however, Mr. O. 

 D. Allen, of Ashford, Washington, by special request, dug up 

 some entire specimens with the result that the mycorhizas were 

 preserved, and are shown in Figure i. 



This species is noted as a parasite in systematic texts, but the 

 author has failed to find any direct evidence of its nutritive connec- 

 tion with any other seed-forming species, either by his observa- 

 tions or from the reports of collectors. 



The structural features of the roots agree with those of other 

 mycorhizal forms in the reduction of the absorbing surfaces, the 

 lack of spiral and annular vessels, the formation of tracheids with 

 narrow transverse pits and the radial elongation of the mediocor- 

 tical region. This last named feature has been supposed to be due 

 to the influence of the fungus in mycorhizal roots, but Groom has 

 shown that it may occur in portions of the root unoccupied by the 

 symbiont. Its presence here, in portions of the root not occupied 

 by the fungus, indicates that it is due to the necessities of absorp- 

 tion and use of organic food perhaps rather than to the stimulation 

 of the presence of a symbiotic organism. 



The Rhizome 



The rhizome is an upright stem, slightly compressed, with in- 

 ternodes i to 2 cm. long, from the terminal internodes of which 

 annually arise one or two flower scapes. 



The epidermis is composed of elongated muriform elements 

 with the outer walls slightly convex. No transpiratory openings 

 are to be found. The cortex is ten to fifteen layers in thickness, 

 the cells are ovoid, cylindrical, pitted and separated by spare inter- 

 cellular spaces. The starch stored here during the resting season 

 is usually exhausted in the formation of the inflorescence. The 

 pericycle is two or three layers in thickness, heavily sclerotized 

 and lignified and is interrupted in places by thin-walled elements. 

 The crowded xylem ring contains a large number of scalariform 

 ducts, and some imperfectly differentiated spiral and annular ves- 

 sels, all deeply lignified. The phloem consists of cambiform ele- 

 ments with spare protoplasmic content. The interfascicular paren- 

 chyma shows collenchymatous thickenings in places, and numbers 

 of elongated conducting cells with unlignificd walls are placed 

 near the vessels (Plate 369, Fig. 4). 



