NORTH AND CENTRAL AMERICAN" COMMELINACE^E— HOLM. 171 



the others, and which occur in rows near the sfcomatiferous strata: finally clavate hairs are very 

 abundant and show the same distribution as the short ones. The epidermis is thinwalled on 

 both faces, and is covered by a smooth cuticle. A collenchymatic tissue is developed as a few 

 layers on the dorsal face of the largest veins. There is a homogeneous chlorenchyma of, in trans 

 verse sections, roundish cells with wide intercellular spaces near the ventral face (the inner) of 

 the sheath. Druids, but no raphides, were observed in the chlorenchyma. The stereome is 

 poorly represented, and occurs as a few cells on both faces of the veins, and is more thickwalled 

 on the leptome-side than on the badrome; in no instances was the stereome observed to be sub- 

 epidermal. In regard to the mestome-bundles, these are collateral and of the usual structure, as 

 described above. 



The leaf blade is scabrous on the ventral face and along' the margins; the midvein is thick 

 and very prominent on the dorsal face. Clavate and two-celled, pointed hairs abound on the 

 ventral face, but only the clavate are frequent on the dorsal. Stomata were observed on both 

 faces, but they are most numerous on the dorsal; they are generally surrounded by four cells 

 (PI. VI, fig. 32) or, though seldom, by five (fig. 31); the guard-cells are conspicuously larger on 

 the leaf-blade than on the stem and the sheath. Viewed en face the cells of epidermis are mostly 

 pentagonal or hexagonal, with the radial walls straight, a structure that was observed on both 

 faces of the blade. Examined in transverse sections epidermis consists of a double layer above the 

 middle portion of the blade, covering the midrib, and also above some of the larger veins. But 

 otherwise there is only one stratum of epidermis, and the cell-walls are thin. The epidermis of 

 the lower face consists of a single layer throughout: the cells are thinwalled and very small 

 underneath the veins, but larger between these. 



A collenchymatic tissue of one layer covers the leptome-side of the midvein and of some of 

 the larger, but there is none on the hadrome-side. The chlorenchyma is differentiated into one 

 stratum of long palisades on the ventral face of the blade, and a pneumatic tissue on the dorsal. 

 The palisade-tissue is quite compact; it contains tannin, but no cells with crystals were observed. 

 The pneumatic tissue, on the other hand, is very open on account of the very irregular shape of 

 the cells, and raphides and crystals were observed here. 



The mestome-bundle> are collateral; they possess a colorless parenchyma-sheath, which i< 

 generally thinwalled; a few layers of thickwalled mestome-parenchyina occurs, sometimes, on 

 the leptome-side. or on both the leptome- and the hadrome-side. The primary veins have a large 

 group of leptome, and several wide vessels. 



THE 8PATHE. 



The structure of the spathe is more simple than that of the .stem-leaves. While the ventral 

 face is destitute of stomata and hairs, the dorsal has numerous stomata and short, pointed hairs 

 in abundance; epidermis is thinwalled on both faces and represents the on!}' tissue in the leaf- 

 margins which are grown together, thus the spathe is partly closed. The chlorenchyma is only 

 developed as a pneumatic tissue, which is very open. No collenchyma was observed, but the 

 mestome-bundles are supported by a few strata of thickwalled mestome parenchyma. Druids 

 and single crystals occur in long, narrow cells beneath the epidermis. 



Commelina dianthifolia D. C. 



The ramification of the Shoot. 



The parts underground consist of a few vertical internodes covered by leaf-sheaths and 

 bearing many fleshy, brown roots with slender lateral ramifications. Our dried material showed 

 no stems from the previous year, but it appears, nevertheless, as if the species is perennial. The 

 aerial stem is quite tall, erect, and profusely branched, each branch being terminated by an 

 inflorescence. These axillary shoots bear membranaceous, tubular fore-leaves and show the same 

 89369°— vol 10—11 12 



