168 MEMOIKS NATIONAL ACADEMY OF SCIENCES, VOL. X, NO. 6. 



THE ROOTS. 



The roots are quite long and more slender than in the preceding species; they are very hairy 

 and represent also here a combination of two types, contractile- and storage -roots. The exoder- 

 mis consists of large, pentagonal cells with the radial walls very prominently folded. The cor- 

 tex consists of fifteen layers, which are quite compact and contain large deposits of starch; some 

 cells were noticed to contain tannin. The cortical parenchyma is thinwalled throughout, and no 

 stereomatic strata are developed in this species beneath the exodermis. Endodermis is thinwalled, 

 with the Caspai-yan spots plainly visible; the pericambium is thinwalled and continuous, sur- 

 rounding five short rays of hadrome with the two to three proto-hadrome vessels situated side 

 by side. The leptome constitutes broad groups, and the conjunctive tissue is thinwalled, but 

 occupies only a very small portion of the central cylinder, since the center contains a very wide 

 vessel. 



THE STEM ABOVE GROUND. 



In the uppermost internodes below the inflorescence the epidermis is covered by a thick 

 and smooth cuticle, and the cellwalls, especially the outer, are distinctly thickened: pluricellular, 

 strongly curbed hairs abound, and the stomata are level with epidermis. Beneath epidermis are 

 several isolated groups of collenchyma, separated from each other by narrow rays of the green 

 cortex, which forms also a closed ring of about three layers around the stereome and the 

 mestome-strands. There is also in this species a sheath like an endodermis which separates the 

 stereome from the cortex proper, but it was very thinwalled in ( '. < recta. The stereome is not 

 very thickwalled, but incloses the peripheral band of mestome-bundles completely. The number 

 of mestome-bundles is rather small, there being about sixteen peripheral and a very few located 

 in the pith, and their structure is exactly the same as noticed in the preceding species. The 

 pith represents a very large thinwalled parenchyma, but contained no starch. 



THE STEM-LEAVES. 



The leaf -blade is very hairy on both- faces, especially on the ventral; these hairs are short and 

 clavate or somewhat longer and with the apical cell strongly curved. The cuticle is smooth or 

 wrinkled outside the subepidermal collenchyma. Epidermis has the outer cell-wall slightly 

 thickened on the dorsal face, much less so on the ventral; the lumen of the cells is large on 

 both faces except above the midrib. Stomata abound on the dorsal face; they are level with 

 epidermis and are surrounded by four cells. 



There are hypodermal layers of collenchyma above and below the midrib, which on the 

 dorsal face passes over into a water-storage tissue of thinwalled colorless cells. Similar groups 

 of collenchyma were also noticed at the other large veins. Besides this support of collenchyma 

 the mestome-bundles possess also a little stereome on the leptome-side, separated from the 

 collenchyma by a single stratum of chlorenchyma; a few cells of stereome were, furthermore, 

 observed in the margins of the blade. The chlorenchyma is differentiated into one layer of 

 palisades on the ventral face, very compact and full of chlorophyll, and into a more open 

 pneumatic tissue on the dorsal. Cells with raphides were observed in both of these tissues. 



The mestome-bundles are surrounded by a thin-walled parenchyma sheath and show the same 

 structure as described above for ('. Virginica. 



Commelina hirtella Yahl. 



The Rhizome. 



A rhizome of a flowering specimen is figured on our Plate I. figure 5. It is perennial, 

 horizontally creeping, with distinct, more or less stretched internodes. the leaves of which are 

 membranaceous and tubular, when young. The roots are hairy, somewhat fleshy, but never 

 tuberous; they are sparingly branched and develop in a number of three or five at the nodes, 

 above the insertion of the leaves. The ramification of the rhizome is sympodial. and the lateral 



