T. Holm — Isqpyrum hitematum. 137 



tional rays of secondary vessels, two groups of secondary lep- 

 tome, and a small thinwalled pith. 



Characteristic of the root-system of I. hitematum is thus 

 the occurrence of slender and moniliform roots, in which the 

 increase in thickness is due to the strong development of a 

 secondary cortex, and in which the secondary formations 

 within the stele consist only in two additional rays of hadrome 

 and two strands of leptome, but with no extension of the cen- 

 tral parenchyma, the pith. 



In the Californian I. stipitafacm, which is, also, a member 

 of the section JEvemion, the roots are very different, and we 

 have examined some specimens, although they were not in any 

 very good condition for this purpose, having been pressed and 

 dried. The root-system of this plant consists of a dense ball 

 of tuberous secondary roots like those of Anemonella* but 

 they are much more numerous. A transverse section of a 

 tuberous root of I. stipitatum shows the following structure : 

 Epidermis is very hairy, and covers directly a cortical paren- 

 chyma of about four layers, the cells of which are moderately 

 thickwalled ; then follows a thinwalled endodermis of very 

 small cells. The larger portion of the section is occupied by a 

 ■ homogeneous, thinwalled parenchyma of secondary cortex and 

 a broad, central pith. There are five minute strands of pri- 

 mordial hadrome, which alternate with five much larger col- 

 lateral mestome-strands, all separated from each other by 

 several layers of parenchyma. These mestome-strands are 

 arranged in two concentric bands, but the distance from the 

 center of the stele to the primordial groups of hadrome is 

 only very slightly shorter than that to the secondary strands ; 

 thus it often appears as if the mestome-bimdles, the primary 

 and the secondary, are located in one single band. If we 

 examine the filiform apex of these same roots, we observe the 

 same structure, but with the secondary cortex and the pith 

 much less developed ; the filiform lateral roots, on the other 

 hand, show a cliarch structure with no signs of secondary 

 formations. 



The rhizome. 



The rhizome of I. hitematum is very slender, and the 

 structure is rather weak. The cells of epidermis are very 

 small and thinwalled ; the cortex consists only of six layers, 

 which are more or less collapsed. There is no endodermis, 

 but a sheath of five strata of collenchyma surrounds the 

 stele ; in some specimens we observed two or three strands 

 of typical stereome located in the collenchyma ; thus the peri- 



*The author: Anemonella thalictroides (L.) Spach. (This Journal, vol. 

 xxiv, September, 1907, p. .243.) 



