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450 BOTANICAL GAZETTE [December 



STEM 



The stems are angular to narrowly winged, densely covered 

 with glandular (fig. 8), long, unicellular, and pointed hairs; the 

 glandular hairs contain free oxalic acid, according to Van Tieghem. 

 The stem structure in general is quite firm, owing to the pres- 

 ence of hypodermal collenchyma and pericyclic stereome. The 

 cuticle is thick, longitudinally wrinkled, and the outer cell wall 

 of epidermis moderately thickened (figs. 16, 17, Ep). Corre- 

 sponding with the angles or wings are hypodermal strands of 

 thick-walled collenchyma (fig. 17, Coll), and the cortical paren- 

 chyma is compact, about three layers, filled with chlorophyll. 

 There is no endodermis, but a distinct continuous pericycle, which 

 forms arches of stereome, but is only distinct in the older portions 

 of the stem. In young internodes (fig. 15) the pericycle is so 

 thin- walled that it is barely distinguishable. There are about 

 nine primary mestome strands, which are collateral, and separated 

 from each other by meristematic strata in young internodes. 



In this meristem secondary formations arise by means of an 

 interfascicular cambium (fig. 16, Camb), which begins from the 

 sides of the mestome strands. As shown in fig. 16, a small strand 

 of leptome (L) is the first product within this meristem, and later 

 on the cambium continues to develop secondary hadrome, that is, 

 porous tracheids and libriform (fig. 18, H). The pith is thin- 

 walled, and not starch bearing, but large spheric crystals were 

 observed, the material having been preserved in alcohol. Similar 

 crystals also occur in the cortex of the old internodes. While the 

 structure of a young internode shows no secondary formations, in 

 the mature stem a compact stele is found in which thick-walled 

 libriform is very conspicuous, developed from the interfascicular 

 cambium. 



Finally may be mentioned that the epicotyl of the young 

 seedling is glabrous, with a smooth cuticle, but without collen- 

 chyma. The cortex is very thick, about twenty layers, and an 

 endodermis is developed outside twelve arches of pericyclic stere- 

 ome, corresponding with twelve collateral mestome strands. No 

 secondary formations occur at this stage. 



