1891.] Anatomical Characters of N. Am. Graminece. 281 



ilarity, easily distinguished from each other by the following 

 anatomical characters, taken from the leaf-blade: 



Epidermis. 



T , . • .u • f 3 P - refractum. 



1 horn-shaped expansions on the superior race -. p c a ]if orn i cum . 



Epidermis of the inferior face perfectly smooth P. Sabinei. 



Epidermis of the inferior face with dwarf cells in alterna- 

 tion with long, rectangular ones P- Califormcum. 



(P. refractum. 

 btomates present on both faces -j p Californicum. 



Stomates present merely on the superior face P. Sabinei. 



t (P. refractum. 



Stomates surmounted with warts \ p s aD inei. 



Mes to m e- bun dies . 

 Midrib forming a sharp carene on the superior face of the j P. Californicum. 



blade : I p - Sabinei. 



( P. refractum. 

 Mestome-sheath thick-walled in the largest bundles j p Californicum. 



(P. refractum. 

 Leptome and hadrome separated in the largest bundles -j p Californicum. 



A few not very thick-walled cells between the leptome and 



hadrome of the largest bundles ' P. Sabinei. 



MesophylL 

 Forms two separate groups, one on each side of the midrib P. refractum. 



Stereo me. 



One isolated group opposite each of the two groups of bulli- 



form cells P - retractum - 



Three isolated groups opposite each of the two groups of 



bulliform ceils. . . . . . P. Californicum. 



One isolated group above each lacune P - refractum. 



One isolated group below and three above each lacune P. Californicum. 



Lacnnes. 



Bordering on the parenchyma-sheath of the mestome-bundles P. refractum. 



Separated from the parenchyma-sheath by a small layer of J P. Californicum. 

 mesophyll < F baDinei. 



U. S. National Museum, Washington, D. C. 



Explanation of Plates XXIII and XXIV. 



Figs. i-Z t DistickIis m*ritim*X— Fig- *• Transverse sec tio n of half of the 

 leaf. The black part of the figure represents the mssophyU, X 75- * 'g . 

 Transverse section through the midrib, X 560 -Fig. 3- Transverse section 



through a small mestome-bundle, X S^ 3 - ^ ~*i~% r,f thp 



Figs. 4-5. Pleuropogon Calif ornicum .-T\%. 4- Transverse section of the 

 middle part of the blade, X 75--^- 5- Transverse section through the raid 



n Fip. 5 t 9 . Pleuropogon refractum .-Tl%. 6. Transverse section through 

 midrib, X 5 6o- Fig 7. Transverse section through f^f 11 ™f to ™f: bun £ !' 

 X56o.-Fig. 8. Transverse section of the middle part of the blade, X75--** 

 9- Epidermis of the superior face, X 240 , , f * 



Figs .0-12. Pleuropogon Sabinei.-?*. 10. Transverse section of half ot 

 blade, X 75-— Fig. n. Transverse section through midrib, X 500.— ng- 

 Transverse section through a small bundle, X 5°° 



