156 MISSOURI BOTANICAL GARDEN. 



pubescence of the leaflets, the degree of persistence of the 

 leaves, the form of the calyx and the presence or absence of 

 glands at its base, the color of the petals and stamens, the 

 number of groups of filaments and the form of the anthers, 

 and the presence or absence of hairs at the base of the 

 style and on the seeds, all appear to afford characters by 

 which species may be recognized, when they shall have been 

 brought together. Unfortunately, herbarium material is 

 rare and as a rule poor, few comparative field studies have 

 been made, and no complete collections occur in conserva- 

 tories, so far as I can learn. Some difference of opinion 

 also exists as to the limitation of this and related genera. 



If the characters given by Don are reliable, our plant is 

 pretty certainly excluded from all of the species described 

 by him, excepting P. affinity the leaves of which are un- 

 known (hence presumably absent at the time of flowering), 

 while the peduncle appears to be longer than in our plant, 

 and the petals erect, — neither of which characters need of 

 necessity exclude our plant; but several important points 

 are not mentioned in the description, so that I should hes- 

 itate either to call it ajjinis or to venture on a new name 

 for it. 



The five species which have been most cultivated may be 



separated by the following key, the names employed 



being those of the Index Kewensis, i. 442, though a strict 



investigation of the synonymy will suggest the propriety 

 of certain changes. 



* Stamen tube divided into live clusters : petals white or greenish. 

 Calyx very brown pubescent: glands present: stamens white: style 



white (or reddish?) 



P. alba. 



Less rusty : no glands : style red. 



Stamens creamy white. P. stenopetala. 



Stamens green below, red above P. minor. 



** Stamen tube divided into ten clusters. 



Corolla and style red: no glands: stamens white, or yellow at 

 base P. insignls. 



Corolla green and white: glands present: stamens and style 

 white P. sp. (plate 27) . 



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