78 



MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



[vol. 10 



at least in places. In the section shown (fig. 36) three main veins, with fibrous 

 sheaths, are present, and ehloroplasts are present in the mesophyll parenchyma, 

 although they are rather sparse. 



2. A. acicularis (fig. 26). Leaves of this species are similar to those of 

 A. acaulis. A section approximately halfway along' the length of the leaf (fig. 

 26) reveals three veins, each surrounded by selerenchyma and embedded in 

 chloroplast-free parenchyma cells isodiametric in transaction. Cells rich in 

 ehloroplasts form a layer immediately beneath the epidermis on both surfaces. 

 Between the veins, pockets of collapsed parenchyma cells occur. A thick-walled 

 hypodermis occurs in the most apical portion of the leaf, where the mesophyll is 

 composed of spherical chlorenchyma. 



3. A. americana (fig. 25). This leaf shows little differentiation from base to 

 apex, except for reduction in number of veins. Especially prominent are the 

 longitudinal zones of collapsed parenchyma. Some of the smaller bundles lie in 

 these zones. All of the bundles are completely ensheathed by selerenchyma. The 

 parenchyma is composed of cells, isodiametric in transection, with relatively few 

 ehloroplasts. These cells may be weakly differentiated as a hypodermis in the 

 adaxial portion of the leaf. The leaves of A. americana are certainly within the 

 range of variation of Abolboda, but an additional similarity may be noted to 

 leaves figured by Arber (1925) for Eriocaulon s&pt angular e. 



4. A. ciliaia (figs. 27, 35). An extensive series of transections of a leaf of 

 this species showed the nature of differences, characteristic of A. ciliata, between 

 base and apex. The most basal portion (leaf sheath) consists only of thin-walled 

 parenchyma in which approximately seven bundles, without fibrous sheaths, are 

 embedded. In the upper portion of the leaf sheath, sclerenchymatous sheaths 

 are present and collapsed parenchyma cells occur between veins, resembling the 

 condition shown for A. acaulis in figure 31. The margins of the leaf at this level 

 are biseriate. Segments of this wing split off, forming the " cilia" implied in 

 the species name. Above the level of the sheath, (fig. 27), the leaf is markedly 

 thicker, lacks tapered margins, and has a hypodermis, one or two cells thick, 

 on the adaxial face of the leaf. The mesophyll (other than the pockets of col- 

 lapsed cells) consists of spherical cells with numerous ehloroplasts. Seven 

 bundles, each surrounded by a sclerified sheath, are present at this level. At 

 higher levels, such as that shown in figure 35, the outermost bundles are not 

 present. *At the margins of the leaves, a portion of the hypodermis, which ex- 

 tends around the edges of the leaf toward the abaxial surface, consists of 

 sclerified cells. At this uppermost level, the chlorenchyma cells are differen- 

 tiated (mostly by relative size of intercellular spaces) into palisade and spongy 

 tissue. The level shown in fig. 35 is notable for the greater thickness of the leaf, 

 a thickness due not only to the greater number of hypodermis layers, but to 

 the greater number of chlorenchyma layers as well. 



Larger-stemmed Abolbodas. 



Despite certain distinctive features in the leaf of A. linearifolia, there is 

 agreement among A. linearifolia, A. macrostachya, and A. sprucei in the follow- 

 ing respects : leaves thicker and larger than those of the above group ; hypo- 

 dermis present, consisting of 3-5 layers of cells; parenchyma like that of the 

 hypodermis (polygonal in transection, markedly elongate in longitudinal sec- 

 tion) also present and bundle sheaths (surrounding fibrous bundle-sheath layers) 



