﻿This is fortunately supplied by the specimens collected by Salle 

 at Cordova.* The specimens from Arizona and the other Mexican 

 specimens listed above lack carpocephala but show clearly the 

 vegetative characters of the species. 



Sullivant's original account, which is reproduced with but 

 slight alterations by Underwood, describes the more striking 

 characters of the plant but does not call attention to the structure 

 of the epidermis and of the ventral scales. These deficiencies 

 are partly supplied by Stephani, who states that the epidermal 

 pores are slightly convex and surrounded by two to three concen- 

 tric series of cells with six cells in each series and that the append- 

 ages of the scales are constricted at the base, ovate, acute, and 

 entire. In her discussion of Aytonia jantaicensis, Miss Haynes 

 notes that the concentric series of cells around the pores of P. 

 Wrightii are composed of from five to eight cells each, instead of 

 being uniformly composed of six cells, as Stephani'a description 



The epidermal pores in P. Wrightii agree in all essential 

 respects with those of P. crenulatum, except that the radial walls 

 tend to be more distinctly thickened. The epidermis is further 

 distinguished by its somewhat smaller cells and better developed 

 trigones and by the presence of a waxy cuticular covering, these 

 features being apparently associated with a more xerophytic 

 habitat. 



Although Stephani's description implies that the ventral 

 scales bear a single appendage it is not unusual to have two such 

 appendages present. They are characterized by their ovate- 

 lanceolate form and acute or obtuse apices, the margins being 

 usually entire and the cell structure fairly uniform. The appen- 

 dages are somewhat constricted at the base, but the constriction 

 often appears more marked than it really is on account of the 

 folds in the basal portion. The marginal cells of the basal por- 

 tion (Fig. 6, D) are more or less irregular and contorted and show 

 vestiges of slime-papillae. 



As pointed out by Miss Haynes, P. Wrightii is related to P. 

 jamaicense. She finds differences, however, in the epidermal 



* It may be noted that Berkeley in his Introduction to Cryptogamic Botany 



