518 MacDougal: Symbiosis and Sapkopiiyti: 



ISM 



u-ith the micro-spccti-oscopc. The free portion representing the 

 lamina is i to 2 cm. in length, and the outer dorsal surface is pro- 

 vided with stomata, the guard cells of which are motile and con- 

 tain starch (Plate 369, Fig. 5). The possibility that the guard 

 cells may contain a small amount of chloroplndl is not excluded 

 though it could not be detected b)' ordinary tests In the specimens 

 exannncd. The epidermis is composed of murlform cells with the 

 outer walls convex and not cuticularized. The mesophyll consists 

 of two layers of irregularly globoid elements rich in protoplasm 

 and separated by large air-spaces. A third layer of thin-walled 

 elements, cyh'ndrical hi form arc to be found lateral to the simple 

 fibrovascular bundles. This tissue is devoid of protoplasm and 

 may serve for the storage of water. The sclerenchyma sheath is 

 mcomplete at the point of contact with this supposed storage tis- 

 sue, thus permitting the ready passage of water between thexylem 

 and the thin-walled cells. 



Tlie degeneration of the leaf is seen to consist in the loss of 

 chlorophyll, the lack of differentiation of the mesopliyll and the 

 reduction of tlie surface. This degeneration has been accompanied 

 by the dex'elopment of a tissue for the storage of water, and by the 

 retention of tlie .stomata. Ccphalauthcra is to be added to the list 

 of chlorophylless species furnished with motile stomata. 



GeNER.VL CONSIDKRATIONS 



It is evident that the mycorhiza of Ccphalanthcra is to be con- 

 sidered as adventitious or accidental in its occurrence. In a large 

 number of cctotropic forms the fungus gains entrance to the un- 

 derground organ very early in its development, and then keeps 

 pace with its growth. In this instance, however, it is found only 

 in certain regions, and might be mistaken for a parasite were it not 

 for its characteristic vesicles or organs of interchange. The com- 

 paratively small area of the mycorhlzal structures suggests that 

 Cephalanthcra is capable of absorbing largely from the humous 

 products independently. 



Calypso rulbosa (L.) Oakes 

 The author has called attention to the occurrence of adventi- 

 tious mycorhiza in Calypso {ix\:,n^\ cited Lundstr6m's description 



