s 



MacDougal: Symbiosis and SAPRoriiYTiSM 519 



of these formations, which have been found by him and others in 

 Europe and America. Since that paper was sent to the press a 

 shipment of plants has been received, which had been collected 

 in northwestern United States, and a number of the specimens 

 showed the coralloid mycorhiza. A careful reexamination has 

 been made of these structures in the light of the generalizations 

 drawn from previous material, and the results are presented below. 

 The subterranean stem of Calypso consists of an ovoid taper- 

 ing corm 1.5 to 2 cm. in length, comprising two or three inter- 

 nodes. The single ovate, or ovate-cordate leaf is terminal, while 

 the inflorescence arises from the first node below. The plant is 

 reproduced vegetatively by a short offset of such reduced length 

 that the new corm formed from its apical intcrnodes stands upright 

 in contact with the old corm (Plate 367, Fig. 6). The few short 

 roots arising from the base of the corm are mycorhizal as de- 

 scribed in the previous paper. 



Stem-mvcoriiiza 



The old or spent corms of the preceding season's acti\ ity may 

 give rise to offsets from the basal internodes, and these may de- 

 velop into coralloid structures by the repeated branching due to 

 the development of all the buds, as in Aplcctnim. The general 

 anatomy of the coralloid formations is too nearly like that of the 

 stem-mycorhizas of Aplcctnim to warrant description here. 



The fungus is seen to be a loose skein of hyphae in the three 

 or four outer layers of the cortex passing outwardly through the 

 thin-walled epidermal cells into the substratum, and do not, so far 

 as observations go, traverse through the nodal trichomes. In this 



respect Calypso differs from other coralloid plants. Occasionally 

 small globular or ovoid structures resembling sporangioles are to 

 be found terminating the branches of the hyphae in the outer cor- 

 tex. The three or four layers of the medio-cortcx are filled with 

 dense masses of interwoven hyphae. The hyphae form irregu- 

 larly swollen branches upon entering the cells of this region, and 

 one or two of these branches near the nucleus of the cortical cell 

 expands into a vesicle, which in turn gives off a large number of 

 branches nearly filling the cell. The hyphae are unseptate and 

 have definite heavy walls. The form, irregular outlines and in- 



