ANATOMY OF MUHLENBERGIA. 



287 



Fig. 36.— Muhlenbevyia filipes— portion of 

 mestome bundle. Transverse section 

 of Made, showing a part of the Ieptome 

 (Lept.), the parenchyma sheath (P), 

 the chlorenchyma (Mes.), and the col- 

 orless parenchyma (Pa.) between the 

 mestome bundles. Scale (i()0. 



thick-walled, colorless parenchyma which separates it from the mes- 

 tome sheath. 



Chlorenchyma (fig. 3G) consisting of small, branched cells with small 

 intercellular spaces in a single layer radially arranged about each 

 mestome bundle, lying only at the sides 

 of the larger bundles, but extending 

 in horseshoe form around the ventral 

 (hadrome) portion of the smaller ones. 

 Parenchyma sheath of the mestome 

 bundles, where adjoining chloren- 

 chyma, also containing chlorophyll. 



Colorless parenchyma (fig. 36) occu- 

 pying the larger ventral ridges (over 

 the larger mestome bundles), and in 2 

 or 3 rows of cells between each 2 nerves, 

 extending from the ventral to the dor- 

 sal furrows. Also in 1 or 2 rows sepa- 

 rating the chlorenchyma from the pa- 

 renchyma sheath of the smaller bun- 

 dles. 



Mestome bundles (fig. 36) with a large- 

 celled parenchyma sheath; mestome 

 sheath none, but mestome parenchyma 

 with cell walls (especially the inner) much thickened, surrounding the 

 larger nerves, simulating a mestome sheath; many of the companion 

 cells in the Ieptome very thick-walled. 1 



1 The two species of Muhlenbergia most nearly allied to M. filipes are M. capil- 

 laris (Michx.) Kunth and M. trichopodes (EH.) Chapm. Chapman regards M. 

 filipes as a variety of M. capillar™, but the striking histological differences, together 

 with good morphological characters, show that in M. filipes we have a perfectly 



valid species. 

 A comparison of the leaf anatomy of the three forms gives some very interesting 



results: 



(a ) M. capillaris is a plant of dry sandy or rocky (eugeogenous) soils, but the leaf 

 shows only feebly the strong xerophy tic structure of M. filipes. Material from Great 

 Falls, Md", was studied. Leaf thinner than inM. filipes, conduplicate when dry, but 

 flat when well supplied with water. Ventral face not furrowed, furrows on the 

 dorsal face extending nearly halfway through the leaf, with stomata at bottom. 



Epidermis much as in M. filipes, but with bulliform cells between each 2 nerves; 

 hairs much fewer than in filipes, all short, thick- walled, pointed, and prickle-like, 

 occurring on the ventral face only above the nerves, on the dorsal face lining the 

 stomata-bearing furrows and there thicker- walled, with hardly perceptible lumen. 



Subepidermal stereome in flattened supporting strands above and below the 

 mestome bundles, from which they are separated by thickish-walled, colorless 

 parenchyma; and also in the leaf margins. 



Chlorenchyma as influx's, but entirely surrounding the smaller bundles, inter- 

 rupted by colorless parenchyma above and below the larger ones. Also much 

 chlorophyll in the cells of the parenchyma sheath which adjoin the chlorenchyma. 



Mestonle bundles with no true mestome sheath, but mostly surrounded by a sin- 



