NORTH AND CENTRAL AMERICAN COMMELINACELE— HOLM. 183 



occur, however, only on the ventral face of the blade. No collenchvnia and no stereome was 

 observed, and the chlorenchyma represents a homogeneous tissue of mostly roundish cells, tilled 

 with chlorophyll and raphides. The veins arc very tine and possess no mechanical support. 



Tradescantia micrantha Torr. 



The stems are weak, decumbent, and often rooting at the nodes. The small, ovate leaves are 

 alternate, and the species reminds very much of the former, T. Floridana, in respect to its habit. 

 The roots, about live at each node, are very thin and show several minute ramifications; they are 

 not confined to the one face of the nodes, but develop all around these. The stems are profusely 

 branched, and the axillary branches begin with a fore-leaf, which is membranaceous, very short, 

 tubular, and truncate. In regard to the axillary buds, these do not break through the sheath of 

 the supporting leaf, and the diagram of the shoot with its leaves and inflorescence corresponds 

 with that of Tradescantia rosea, as described in the preceding. 



In some of the specimens which we have examined the lateral branches bore a number of 

 leaves, developed as mere sheaths with minute blades, as if they were subterranean. 



Tradescantia Warszewicziana Kunth et Bouche. 



This remarkable Tradescantia is figured in Curtis's Botanical Magazine." and one of the 

 figures shows an entire plant with "the stem stout, forked, terete, having a subarborescent 

 character, and marked with the scars of fallen leaves. The branches are leaf}', chiefly toward 

 the apex/' The peduncle is figured and described as ""axillary, 1 to 1£ feet long, terete, purplish 

 above, fcniing a not very copiously branched panicle of purple-lilac densely crowded but small 

 flowers." The habit of the plant, considering the stem and the foliage, is thus much more like 

 that of an Aloe or a Draca mi than of a Tradescantia. The internodes of the stem are exceedingly 

 short, and the leaves are crowded. The relatively short and compact inflorescence is borne upon 

 a long, naked scape, which is axillary. The bracts that subtend the inflorescential branches are 

 very short and broad. In regard to the flowers, the sepals and petals are uniform and purplish, 

 the latter the largest; the stamens are all uniform and beardless. In spite of these very pronounced 

 habital characters the .species is by Clarke placed in his section: Eutradescantia; we do not 

 consider this classification a natural one, for even if the floral characters may be identical, to some 

 extent, the habit of the plant in connection with certain points in its anatomical structure make 

 us believe that the species really represents a section of its own. 



With Planchon our species was a Dichorisamlra; with Hasskarl a Spirmn ma (fide Clarke 1. c. ). 



The Internal Structure of the Vegetative Organs. 



the ROOTS. 



Numerous long, whitish and somewhat fleshy secondary roots are developed from the 

 nodes, and they are amply ramified. Their structure is as follows: 



The epidermis is very hairy, and there is an exodermis of one layer of pentagonal cells with 

 the outer walls moderately thickened, and with the radial walls very distinctly folded. Cortex 

 consists of about ten layers of thinwalled cells arranged radially toward endodermis. No starch 

 or raphides were observed. The endodermis is thickwalled in the manner of an U-endodermis 

 and is very porous. A thinwalled, continuous pericambium surrounds sixteen short rays of 

 hadrome with some narrow (spiral) and a few wider (reticulated) vessels; the proto-hadrome- 

 vessels were noticed to be single in each ray. The leptome is well developed and represents 

 round groups in transverse sections, with the proto-leptome cell plainly visible. The center of 

 the root is occupied by a narrow group of thickwalled conjunctive tissue. 



a Vol. 16, Tab. 5188. 



