520 MacDougal : Symbiosis and Sapropiivtism 



definite membranes of the hyphae in the medio-cortex led Lund- 

 strom to believe that the funi,nis was plasmodial In its earlier 

 stages (9). This appearance is heightened by the adhesion of the 

 cytoplasm of the cortical cell to the hyphae. The inner cortex is 

 free from hyphae, and contains starch in abundance, especially in 

 the apical region. Starch is also present In the outer cortex, but 

 quickl)' disappears from the cells iiu'aded by the hyphae. The 

 nuclei of the outer cortical cells arc nearly normal, but those of 

 the medio-cortex, occupied by the fungus, are hyperchromatic, 

 distorted, and in some instances undergo fragmentation, as in 

 Pcraminiii {\\). The stele is not differentiated Into xylem and 

 phloem, and consists chiefly of cylindrical elements rich in pro- 

 toplasm, not differing greatly from plcrome. The endodermis 

 cannot be made out. The fungus of the coralloid structure and 



that of the roots are quite similar, but their identity is not es- 

 tablished. 



A comparison of the specimens which have come under inspec- 

 tion makes it apparent that the tendency to form coralloid myco- 



rhizas 



coral I 



4- 



xlypso as in Aplt 



the base of corms two years old, while in others their bulk was 

 greater than that of the corm of the previous season to which they 

 were attached. The extreme development was found in one 

 specimen in which the coralloid structure was very large, and the 

 old corm to which It was attached was shrunken to half its orig- 

 inal .size, but was still sound and normal (Plate 367, Fig. 8). A 

 second offset had sprung from the node nearest the apex of the 

 corm. This offset was about a centimeter in length and bore two 

 roots at the first node while the three upper Internodes had begun 

 to swell in the formation of a new corm. The terminal portion 

 bore a rounded cordate leaf and a flower bud. The members of 

 this specimen named in order from the basal end were : stem- 

 niycorhiza, spent corm, offset, roots, developing corm, flower bud 

 and leaf A comparison of the specimens at hand showed a fairly 

 well established correspondence between variation in the outline of 

 the leaf and the development of the stem-mycorhiza. Such varia- 

 tion might be due to the increased capacity of the plants furnished 

 with coralloid structures for the absorption of humus products. 



