178 MEMOIRS NATIONAL ACADEMY OF SCIENCES, VOL. X, NO. 6. 



But in its natural .surroundings, in woods or among rocks on the river-shores, the plant does not 

 show such profuse development of shoots, and the rhizome is consequently much less branched. 

 However, the principal features of the structure are identical, and the following characteristics 

 may be mentioned: The rhizome is at Hist creeping, and during the life of the plant some of the 

 shoots develop in this manner with horizontal internod.es, while the majority of the buds under- 

 ground develop immediately into ascending shoots. The internodes of the rhizome are usually 

 short and densely covered with membranaceous, sheathing leaves like the base of the aerial stem. 

 All these leaves subtend axillary buds, and the biseriate arrangement of the leaves is readily 

 recognized by the very regular position of the buds upon the rhizome in two rows. The root- 

 system is represented by numerous fleshy though rather slender roots, which develop from all 

 sides of the nodes. 



The Internal Structure of the Vegetative Organs. 

 the ROOTS. 



The secondary roots are quite long, rather slender and sparingly branched; their color is 

 dark brown, and their surface shows a very pronounced wrinkling. They represent a combination 

 of contractile- and storage-roots. Lateral roots occur, but these are mostly filiform and of short 

 duration. 



In the secondary roots the epidermis is thinwalled and hairy: it becomes suberized at an 

 early stage and covers the old roots as a stratum of partly collapsed cells. Inside the epidermis 

 is an exodermis of a single layer, the cells of which are thinwalled and in which the radial walls 

 are very prominently folded (PI. VII, fig. -±3). The cortical parenchyma consists of many strata 

 of thinwalled cells with distinct intercellular spaces and sometimes with lacunes near the 

 periphery; deposits of starch and cells with raphides were observed in the cortex. A thinwalled 

 endodermis with the Casparyan spots plainly visible surrounds the central cylinder. The peri- 

 cambium, which is thinwalled, was found to. be continuous in all the secondary roots examined. 

 The hadrome forms about ten rays, of which the innermost vessels are reticulated and very wide, 

 surrounding a central group of thinwalled conjunctive tissue. The leptome is well developed 

 and shows the proto-leptome cell very plainly. 



A similar structure was noticed in the lateral roots, but only in some of these was the 

 exodermis observed. We might also mention that the center of these roots was constantly 

 occupied by a wide reticulated vessel and that the pericambium was interrupted by some of the 

 proto-hadrome vessels. These interruptions appeared, however, as being very irregular; in 

 lateral roots of first order one proto-hadrome vessel out of six rays had broken through, while 

 in lateral roots of second order two vessels out of four rays were bordering on endodermis. 



THE STEM ABOVE GROUND. 



The basal internode is smooth and glabrous. A thin, smooth cuticle covers the epidermis, 

 of which the outer and partly also the radial cellwalls are somewhat thickened. About four 

 strata of thickwalled collenchyma separate epidermis from the cortex, which constitutes about 

 six quite compact layers, rilled with chlorophyll and some raphides. Inside the cortex is a 

 closed sheath of stereome in one to two layers, which surround the niestome-bundles. These are 

 arranged in three almost concentric bands; those of the peripheral band border directly with 

 their leptome on the stereome. They are often approximately perihadromatic, due to anasto- 

 moses, and the hadrome contains several wide reticulated, some narrower scalariform, besides an 

 annular vessel in a lacune. The niestome-bundles of the innermost two bands are not so numer- 

 ous as the peripheral; they are mostly collateral and are very conspicuous by containing large 

 lacunes with remnants of annular vessels. "Thyllen" were frequently observed in these vessels. 



The mestome-strands are thus located in the pith, and none of these were surrounded by 

 parenchyma- or by mestome-sheaths. The pith is thinwalled, and shows very distinct intercellu- 

 lar spaces; cells containing raphides were observed in the pith, but no starch. 



