72 



MEMOIRS OF THE NEW YORK BOTANICAL GARDEN 



[VOL. 10 



Smaller-stemmed Abolbodas. 



The four species, A. acaulis (fig. 9), A. acicularis (fig. 10), A. americana, and 

 A. ciliata (fig. 11), that are considered under this category show four features: 

 (a) the bundles other than those that are leaf traces are most often enclosed in 

 a sclerenchyma cylinder; (b) sclerenchyma ensheaths departing leaf traces indi- 

 vidually; (c) the ground tissue of the stem (other than sclerenchyma) consists 

 of more or less spongy tissue lacking in starch; and (d) the bundles (except 

 leaf traces) are present in a cylinder and no bundles are present in the central 

 portion of the stem. The variations on this pattern are as follows. 



1. A. acaulis (fig. 9). In this species, departing leaf traces are most often 

 incompletely sheathed with sclerenchyma ; such sclereids are few or absent at 

 the outer (phloem) pole. Centrally placed in the core of parenchyma is a nest 

 of sclereids. This nest of sclereids occurs along the length of the stem, and is 

 present even in the most basal region, where other sclerenchyma is wholly 

 lacking. 



2. A. acicularis (fig. 10). The central portion of the stem, including bundles 

 other than leaf traces, is sclerified. Sclerenchyma forms a conspicuous sheath 

 around leaf traces; it is more abundant at the xylem pole of each bundle. The 

 bundles other than leaf traces form a single ring. Sclerenchyma may form a 

 cylinder, as illustrated, may occupy the entire central portion of the stem, or 

 may, as illustrated for A. acaulis, form a nest within the ring of bundles. The 

 latter condition occurs in the base of the stem, and the cylinder is characteristic 

 of the upper portion of a stem. 



3. A. americana. Sclerenchyma (other than that which forms a cylinder in 

 the center of the stem) is present only at the xylem pole of departing leaf traces. 



4. A. ciliata (fig. 11). This species shows essentially the same features as 

 A. americana, although the stem is somewhat larger. 



Larger-stemmed Abolbodas. 



This group includes A. linearifolia (fig. 12), A. macrostachya and its vari- 

 eties (fig. 13, var. angustior), and A. sprucei (fig. 14). These species agree in 

 possessing (a) much wider stems than species of the above group ; (b) no scleren- 

 chyma other than individual sheaths on bundles; (c) compact, never spongy 

 ground tissue, often differentiated into a starch-poor zone outside and an inner 

 coro (figs. 12, 13, inside dotted lines) which contains numerous elongate starch 

 grains; %nd (d) bundles throughout the central portion of the stem, more 

 numerous in a cylinder just inside the outer limit of starch-rich tissue. In all 

 preparations, the ground tissue consists of more or less isodiametric cells asso- 

 ciated with relatively small intercellular spaces. Starch may be expected to vary 

 in amount depending on the state of development of the plant. Variations with 

 respect to species are as follows. 



1. A. linearifolia (fig. 12). Many of the bundles lack sclerenchyma. Where 

 present, it takes the form of a semicircle at the interior pole of the bundle. 

 Sclerenchyma is associated wi v th the larger bundles, and may be an indication of 

 major bundles which enter leaves a short distance above the level of sectioning. 



2. A. macrostachya. In A. macrostachya var, macrostachya and var. roous- 

 tior, the same condition described for A. linearifolia was observed. In A. macros- 

 tachya var. angustior (fig. 13), however, all bundles were found to be associated 

 with sclereids, which may be quite abundant near some bundles. Some leaf 

 traces are completely ensheathed by such sclerenchyma. 



