NORTH AND CENTRAL AMERICAN COMMELINACEiE— HOLM. 185 



A transverse section of the blade shows the following- structure: Epidermis consists of rathei 

 low cells on both faces (tig. -±7), and the thickening of the outer walls is very distinct in some of 

 the cells; the stomata are level with epidermis, and the air-chamber is wide, but shallow. Under- 

 neath the ventral epidermis is a large water-storage-tissue, which occupies the entire upper face 

 of the blade without being interrupted by the chlorenchyma or by any strands of mechanical 

 tissue. It reaches its highest development above the middle portion of the blade and decreases 

 in thickness toward the margins. This water-storage-tissue consists of three layers of cells that 

 are much larger than those of epidermis: the innermost layer is the thickest on account of the 

 greater height of the cells. When exposed to a dry atmosphere the cells of this tissue shrink 

 rapidly by foldings of the radial cell-walls. A like tissue, but of smaller dimensions, occurs 

 also beneath the dorsal epidermis. The chlorenchyma is differentiated into one to two layers 

 of short palisades on the ventral face and a larger pneumatic tissue on the dorsal. The 

 palisades are best developed near the margins of the blade where the water-storage-tissue is not 

 so thick. The cells of the pneumatic tissue are somewhat irregular, more or less star-shaped, 

 and they contain much chlorophyll. Cells with r aphides were observed inside the ventral 

 water-storage-tissue and above the palisades. While the chlorenchyma on the ventral face of the 

 blade is completely separated from epidermis by the continuous strata of water-storage- tissue, it 

 does reach the dorsal epidermis by narrow rays, which thus interrupt the colorless-tissue, but 

 only here and there between the veins. The mechanical tissue is weakly developed as an isolated 

 strand of stereome in each margin and as a few layers on the leptome-side of the veins. No 

 collenchyma was observed. The mestome-bundles are collateral and very small; they possess a 

 thinwalled parenchyma-sheath, a small group of leptome, and a few vessels. 



Weldenia c<ni<li<l<< Schtjlt. fil. 



The first description and illustration of this remarkable plant was published in Flora 

 (January, 1829), by J. H. Schultes. jr., who received a specimen from Mexico collected by 

 v. Karbinsky. The genus is dedicated to Baron v. Welden, an Austrian botanist. Ten years 

 later the plant was described by Bentham" as a new genus Lampra volca/nica, and his material 

 came from Volcan de Agua. at an elevation of about 14.0o0 feet, in Guatemala. Since then the 

 plant has been collected in a few other places, in Sierra delas Cruces and Ojo Caliente, Zacatecas, 

 both in Mexico. It is fairly well illustrated by Sir Joseph Hooker.'' but the drawing, which 

 was based upon dried material, does not show the petals correctly. The petals are not spreading, 

 but almost erect in accordance with a photograph taken by Macgraw Coxe, United States 

 minister to Guatemala and Honduras (IsHT). 



The Ramification' of the Shoot. 



The plant is a perennial herb provided with a dense cluster of fusiform roots developed from 

 the basal nodes of the shoot. The shoot is single, judging from the material that has been exam- 

 ined, and consists of a few short or sometimes more or less stretched internodes which bear mem- 

 branaceous sheathing leaves without blades. Two buds, one larger and one smaller, and both 

 evidently dormant, are generally found at the base of the flowering shoot: these buds are situ- 

 ated somewhat lower than the flowering shoot, and they belong to basal leaves of the shoot 

 of the previous year. If we now examine the structure of the flowering shoot of this season we 

 notice (PI. VIII, fig. 49) five membranaceous leaves alternating with each other (/'-/); the inter- 

 nodes, especially the basal, are very short, while the upper ones (between I 3 and I s ) are longer, 

 from two to five cm. in length. Three axillary buds are developed, and these belong to /'. /', 

 and / 3 ; it appears as if the bud in the axil of / 3 is the one that will develop) into a floral shoot dur- 

 ing the succeeding year, and that the two others correspond with the two dormant ones at the 

 base of the shoot of last year's growth. The other leaves of the flowering shoot form a rosette 



oPlantse Hartwegianse. London. 1839. 



&Icones plantarum. S;er. 3, vol. 3, 1S77-1S7H, p. 28, tab. 1236. 



