Rosaceæ. 11 



layers of the latter may occur. The periderm contains fairly 

 large intercellular spaces, which however are always absent 

 from the inner side of the cork-layers. On older parts of 

 the stem the periderm peels off as brown concentric flakes. 



During the first period of vegetation of the shoot is form- 

 ed the greatest amount of the total secondary wood, since 

 often the addition during following years is only a few layers 

 thick. The annual rings are, however, fairly distinct. The 

 structure of the wood is regular, one-layered medullary rays 

 being separated by vessels and tra- 

 cheids in one to a few layers. Some 

 wood-parenchyma is, however, also 

 present. 



The pith is heterogeneous. It con- 

 sists of a broad peripheral part of 

 homogeneous living cells which lasts 

 during the life of the shoot, and in 

 addition of a central part which dies 

 away early. The pith, the medullary 

 rays, the pericambium and the phel- 

 loid tissue are the chief depositories Fig. 2. Potentilla palustris. 

 of food-material, and during autumn ■ and b ' f &nd f ar ^ iIom T , th " 



» lower surface ot a leaf from Den- 



they are filled with starch, but on mark (Bagsværd) ; «%. 

 investigating the shoots in November it will be found that 

 almost all the starch has disappeared and has been replaced 

 by fat the presence of which is indicated by use of Sudan III. 

 In Denmark this change takes place in October. 



The imparipinnate leaves are covered on both sides to 

 a greater or less degree with hairs of the usual unicellular 

 form; older leaves are often almost glabrous. Irmisch (1. c.) 

 writes that in the young plant the leaf-stalk and the margin 

 of the leaves bear stalked glands, and on older plants he 

 found such glands also on the leaves which had developed 

 during spring, while they were absent from the leaves which 



