512 BOTANICAL GAZETTE [December 



there are exceptions, some at least can be shown to be partition 

 cells which have secondarily assumed the character of diaphragm 

 cells (fig. 10). Around storage cells the diaphragm cells frequently 

 assume a rosette arrangement (fig. 16), apparently for conductive 

 purposes. The fact that the first connection of the cross-bundle 

 with the longitudinal bundle is with the phloem also lends weight 

 to this suggestion. Longitudinal sections show that the diaphragm 

 cells extend a short distance into the partitions, and that the ordi- 

 nary polygonal partition cells become elongated and slope toward 



Fig. i6.—Scirpus valid us: & few cells at edge of diaphragm: /, food storage cell; 

 d, diaphragm cells leading to or from storage cell; pc, cortical parenchyma; Xi75- 



the diaphragm, thus suggesting a conductive function (fig. n)« 

 From these conditions it seems reasonable to conclude that con- 

 duction is one function of the diaphragms of Scirpus validus. 



Summary 



i. Diaphragms, although present in many monocotyledons, are 

 not restricted to that group. The present state of our knowledge, 

 however, does not allow us to make definite statements as to their 

 distribution. 



2. Diaphragms are especially characteristic of leaves, but have 

 been reported for all parts of plants except flowers and fruits. 



