246 T. Holm — Anemonella thaUetroides. 



very slight indication of increase in thickness by a few cell- 

 divisions inside the leptome. Otherwise the structure is very 

 primitive. There is an epidermis with numerous hairs, and 

 four strata of thin-walled cortical parenchyma. Endodermis is 

 thin-walled, and the pericambinm consists of one layer outside 

 the leptome, but of two outside the proto-hadrome. Four 

 broad groups of leptome alternate with four rays of ves- 

 sels, which extend to the center of the stele, no pith being 

 developed. 



In the tuberous portion of this same root the structure is 

 very different on account of the large increase in thickness. 

 Epidermis, the cortical parenchyma and endodermis have been 

 thrown off, but replaced by a few strata of pericambial cork ; 

 inside the cork is a large secondary cortex of thin-walled paren- 

 chyma with narrow, rhombic intercellular spaces. The stele 

 now represents eight rays of mestome radiating from the 

 broad central pith. The primordial hadrome is readily to be 

 seen as four very short rays (H in fig. 5, which represents 

 only one-half of the stele), while the secondary rays are longer 

 (JEP) ; outside these secondary rays of vessels are corresponding 

 strands of leptome (L), thus constituting ordinary collateral 

 mestome-bundles. The primary leptome is no longer visible, 

 but three secondary leptomatic strands have become developed 

 outside each of the primary and secondary rays of hadrome. 

 There are thus twenty-four strands of leptome in the tuberous 

 root-portion, but only four of these border directly on had- 

 rome (the secondary); all the others are isolated, but arranged 

 very regularly in eight radii, corresponding with the hadro- 

 matic rays. 



A corresponding structure is to be observed in the slender 

 roots (R, in figs. 1 and 2), and as stated above, these roots 

 become tuberous during the first season. Epidermis and the 

 primary cortex become thrown off very early, but are replaced 

 by the endodermis and a few layers of pericambial cork. A 

 secondary cortex is amply developed at this stage and the stele 

 shows very distinctly four primary and four secondary rays of 

 hadrome. Outside the latter are numerous strata of cambium 

 and groups of secondary leptome. A thin-walled pith occupies 

 the center of these roots. These roots are secondary, and they 

 all grow in a horizontal direction ; their increase in thickness 

 depends upon the formation of a secondary cortex from the 

 pericambinm, and upon the development of secondary mes- 

 tome originating from cambial strata in the shape of arches in- 

 side the primary leptome ; they are not contractile, and possess 

 no exoclermis. It is now interesting to see, that the primary 

 root of the seedling is vertical, that it shows the same manner 

 of increase in thickness as the secondary, and that it possesses 



