CLAYTONIA GRONOV.— THEO. HOLM. 35 



in the axils of which may be developed either inflorescences, vegetative shoots with distinct inter- 

 nodes, or small bulblets. 



However, the stem structure is almost identical, and characteristic of the genus seems the 

 lack of collenchymatic and stereomatic tissue, as mentioned by Becker." The cuticle is always 

 distinct, and is prominently wrinkled in ('. Chamissonis, C. megarrhiza, and C. sarmentosa. In 

 regard to epidermis, we notice in ('. Virginica (PI. 2, fig. 17) an excessive thickening of the outer 

 cell wall, with numerous layerings; in the other species the outer cell-wall is generally thickened, 

 but only moderately. The cortical parenchyma is rather open from the intercellular spaces being 

 quite wide, and the innermost stratum is differentiated as an endodermis, usually thin walled 

 throughout, and showing the < 'asparvan spots very plainly; in ('. arenicola, however, the endo- 

 dermis showed the cell-walls slightly thickened. Inside the endodermis are four very broad 

 collateral mestome-bundles. separated from each other by thin-walled parenchyma, medullary 

 rays; besides that there is a narrow group of this same tissue in the center. 



If we now compare the structure of the rhizomes, we find in the stolons of C. Chamissonis 

 almost the same development of the various tissues as in the stem above ground. But in the 

 stolons the cortex contains deposits of starch, and the endodermis has the inner cell-wall slightly 

 thickened; besides that, there is some thick-walled mestome-parenchyma between the leptome 

 and the endodermis. Of the four mestome bundles, the two are much broader than the others, 

 and the pith seems to be less developed than in the stem. The stolons of this species possess no 

 cambium, and are thus incapable of growing any further in thickness; they are not of any long 

 duration, either, since they evidently separate from the mother plant at the close of the first 

 season, when they are able to continue their growth independently. 



A more developed structure is possessed by the above-ground stolons of C. sarmentosa. In 

 these the cuticle is thick and prominently wrinkled, covering an epidermis of small but somewhat 

 thick-walled cells; the cortex consists of about eight quite compact layers, but without starch. 

 The thin-walled endodermis surrounds a secondary cortex of about six layers, with abundant 

 deposits of starch, inside of which is a closed ring of several collateral mestome-bundles with 

 intrafascicular layers of cambium. The center of the stolon is occupied by a narrow cylinder of 

 starch-bearing pith. In this species the stolons are thus able, to increase in thickness, and our 

 material showed plainly that they remain active and in connection with the mother plant for at 

 least two or three years. 



The horizontally creeping rhizome of < '. asarifolia persists for several years, and shows many 

 layers of cork, forming a thick coating around a broad, starch-bearing parenchyma of a secondary 

 cortex. The mestome-bundles are all collateral and arranged in a circle; they consist of leptome, 

 cambium, and man}' narrow vessels, especially pitted ducts. A very compact, starch-bearing pith 

 occupies the greater portion of the central cylinder. 



In ( . parvifolia there is also a horizontal rhizome, but this is partly above ground, and of 

 a much weaker structure. The epidermis is at length thrown off without being replaced by 

 any layers of cork, while the cortex and endodermis persist; the former of these contains 

 chlorophyll. There are only five collateral mestome-bundles, without cambium, and these are 

 separated from each other by rays of the broad central pith. 



A somewhat greater diversity in regard to the structure is thus observable in the rhizome 

 than in the flower-bearing stems, which is quite natural when we consider the various modifica- 

 tions exhibited by the former, viz: The perennial creeping rhizome of C. asarifolia, the annual 

 stolons of ('. Chamissonis, in contrast to the perennial ones of ('. sarmentosa. 



THE LEAF. 



We meet here with several, and quite important, modifications of structure, which is by no 

 means surprising, when we remember that the leaves winter over in some species. < '. megarrhiza, 

 ('. arctica, and < '. sarmentosa, but die off in all the others before the summer has passed, not 

 speaking of such leaves as are developed as mere bulb scales, in C. Ghamisson'ix, for instance. 



"Becker C: Beitrag zur vergleichenden Anatomie der Portulacaceen. tnaug. diss?. Miinchen, 1895. 



