38 T. Holm — CMonophila Benth. 



almost, been passed by in silence. To obtain a more com- 

 plete idea of the alpine structure and its correlation with 

 the surrounding' medium it will be necessary to include 

 the stem as well as the root structure, and to decide 

 whether certain structural peculiarities may be really 

 epharmonic or inherited. 



Finally with reference to Pentstemoniopsis this plant 

 shows exactly the same monopodial growth as Chiono- 

 phila: a terminal rosette of leaves, axillary floral stems, 

 and axillary stolons. The monochasium is also repre- 

 sented in this plant, and more distinctly than in CMono- 

 phila, since the inflorescence is more open. The seeds 

 also agree with those of Chionophila (fig. 15), but the 

 flower and the fruit resemble those of Pentstemon. The 

 habit of the plant thus corresponds with that of Chiono- 

 phila, the deeply cleft calyx and the free capsule with 

 those of Pentstemon. The corolla with the lower lip 

 bearing short-papillae instead of distinct hairs as in 

 Chionophila is of small importance, but the gibbous base, 

 and the horizontal position of the flower render the plant 

 distinct from both, and especially when combined with the 

 monochasial ramification of the inflorescence. 



Pentstemoniopsis is undoubtedly a good genus, if we 

 include the vegetative characters, and the structure of the 

 inflorescence in the diagnosis. 



EXPLANATION OF FIGUEES. 



Fig. 1. Chionophila Jamesii. Diagram of the shoot; for explanation 

 see the text. 



Fig. 2. The flower, seen from above; enlarged. 



Fig. 3. The fruit surrounded by the marcescent calyx and corolla; 

 enlarged. 



Fig. 4. The capsule removed from the calyx and corolla; enlarged. 



Fig. 5. Cross-section of a secondary root; Ep.=epidermis; Ex.= 

 exodermis; Ph.r^phellogen ; X 320. 



Fig. 6. Cross-section of inner part of same root; C.nzcortex; End.=z 

 endodermis; P.=::pericycle ; L.=zleptome; V. ^vessels; X 496. 



Fig. 7. Cross-section of inner part of stem; S.=:pericycle ; P.=pith; 

 H.:=hadrome; other letters as above; X 320. 



Fig. 8. Ventral epidermis of leaf with a stoma; X 496. 



Fig. 9. Epidermis of stem with hairs; X 320. 



Fig. 10. Dorsal epidermis of leaf; X 496. 



Fig. 11. Pentstemoniopsis Tweedyi (Rose) Eydbg. The flower, side- 

 view ; enlarged. 



Fig. 12. Lower lip of flower; enlarged. 



Fig. 13. The stamens, four fertile, one sterile; enlarged. 



Fig. 14. The fruit; enlarged. 



Fig. 15. The seed; enlarged. 



Clinton, Md., April, 1920. 



