50 



Knud Jessen. 



about 8 mm. thick and about 10 cm. long; they do not branch, 

 but bear thin absorbent roots. During winter they are found 

 crowded with starch which appears to be transformed to fat 

 only in a very slight degree. 



Pot. anserina, like many other plants, has the power of 

 keeping its growing point on a level with the surface of the 

 ground, at any rate if the shoot-apex has been covered with a 

 I layer of earth and in such a case 



the fresh food-storing roots are in 

 the autumn often found to be raised 

 as much as 2 cm. above the re- 

 mains of the shoot-base of the 

 previous year upon a portion of 

 the axis with elongated internodes. 

 Anatomy. In the slender 

 absorbent roots of the first 

 and second order considerable 

 quantities of strong fungal hyphæ 

 occur which form balls in the cells 

 of the loosely built cortex. The 

 epidermis, especially of the ab- 

 sorbent roots of the second order, 

 is very small-celled, very much as 

 in Potentilla palustris, but the 



Fig. 19. Potentilla anserina 

 (Denmark; 28. 9. 1912.). 



Autumn stage; the runners dead or OUtcr Wall is thinner, and the 

 dying; I, the leaf -bases ; d, the dead . 



food-storing root of 1911—12; /, two skm IS collapsed; nor are the dark 



fresh food-storing roots which have ' . i p i • r» . 7 . • 



been developed in the summer of 1912 contents foUnd Ш PoLpoluStriS 



(somewhat reduced). DreSGIlt here 



Fig. 20, A shows the structure of the fully developed 

 food-storing root. On the outside is seen the thin cork 

 with a few fragments of the primary cortex, then follows 

 the thick secondary cortex and lastly a few groups of vessels 

 around the small pith. Not until during the beginning of 

 summer is a continuous woody part developed in the middle 



