NORTH AND CENTRAL AMERICAN COMMELINACEjE— HOLM. 179 



The third internode above the basal bears a green leaf with an axillary, small inflorescence. 

 The structure of the cuticle, epidermis, and collenchyma is as described above, but the cortex is 

 more open. The stereome surrounds here four concentric bands of mestome-bundles, which are 

 mostly regularly collateral. 



The upper internodes are hairy from two-celled hairs, of which the apical cell is very long 

 and pointed, straight or slightly curved, but not hooked as we noticed in Commelina. Stomata 

 abound, and are located in longitudinal rows. They have one pair of subsidiary cells parallel 

 with the stoma. Otherwise the epidermis shows the same structure as in the lower internodes. 

 The cortex is very open and borders outward on a collenchymatic tissue, inward on a sheath of 

 stereome. The mestome-bundles are also here arranged in four almost concentric bands, but are 

 mostly perihadromatic. The pith is thinwalled and not broken. 



THE FLOWERING PEDUNCLE. 



The stem-structure is readily recognized in the peduncle, since the tissues are arranged in 

 the same manner, but developed somewhat differently. Epidermis is much more hairy from 

 very long, pointed hairs, mixed with some glandular. The collenchyma and stereome are both 

 quite thinwalled, and the mestome-bundles occur here in only two concentric bands, of which 

 the peripheral are more or less fused together, two and two. 



THE STEM-LEAVES. 



The green leaves are smooth and glabrous on the ventral, but hairy on the dorsal face. 

 Viewed en face the radial cell-walls of epidermis are straight, not undulate: the hairs are short 

 and pointed. Stomata occur on both faces of the blade, but are most numerous on the dorsal. 

 They are surrounded by four cells, of which the one pair is parallel with the stoma. The guard- 

 cells are mostly raised a little above the surrounding epidermis. Viewed in cross-sections the 

 cells of epidermis are quite large on both faces, especially on the ventral, where it covers three 

 to four strata of colorless thinwalled cells above the midrib. Similar but smaller groups of 

 colorless cells were, furthermore, noticed between the other veins, but only on the ventral face. 

 A collenchymatic tissue of two or three strata is developed below the midrib and the stronger 

 veins, but is entirely absent from the ventral portion of the leaf-blade. 



The mesophyll represents an almost homogeneous tissue of irregular cells with wide inter- 

 cellular spaces. Some few palisade cells were observed, however, on the ventral face, but only 

 in the lateral parts of the blade, and without forming a distinct tissue, ('ells with raphides 

 abound in the mesophyll. especially near epidermis. 



The mestome-strands possess a thinwalled parenchyma-sheath, which does not contain 

 chlorophyll, and is therefore readily distinguished from the surrounding cells of the mesophyll. 

 The midvein is barely larger than the others, but is prominent by its larger support of collen- 

 chyma. The leptome and hadrome are w ? ell developed, and show the usual structure, the 

 mestome-bundles being all collateral. 



Tradescantia scopulorum Rose. 



The Ramification of the Shoot. 



The rhizome is very short and bears many slender, but somewhat Meshy roots, which are 

 almost unbranched; it resembles that of T. Virginica. The aerial stems are erect and branched 

 from near the base. These lateral branches begin, as usually, with an addorsed fore-leaf, tin 1 

 shape of which is quite characteristic; it is membranaceous and consists of u tubular sheath and 

 a very distinct blade, reaching until 15 milimeters in length. This fore-leaf is thus only partly 

 covered by the sheath of the stem-leaf, which supports the lateral branch. The other leaves of 

 the branches are green and alternate with the fore-leaf, showing the same position as described 

 above under Tradescantia rosea. It appears us if the branches become terminated by inflores- 

 cences, but these are usually not so rich-flowered as the one that terminates the main shoot. 



