220 Fr. J. Mathiesen. Primulaceae. 



The mesophyll is on the whole loose in structure. Dode- 

 catheon frigidum has 1 layer, Pr. nivalis 1 — 2 and Androsaces 

 chamaej. 1 — 3 layers of palisades. The leaves of Androsaces sept. 

 vary somewhat in thickness, and show from 2 — 4 layers. 

 The Primula species of the group Farinosae are characteri- 

 sed by having the uppermost layer of the mesophyll com- 

 posed of somewhat irregular, ovate or barrel-shaped cells, 

 with large intercellular spaces, so that a true palisade layer 

 can scarcely be said to have developed. Pr. jarinosa in 

 the Alps shows, according to Wagner, the same peculiarity. 

 In the case of Androsaces chamaej. and Dodecatheon frigidum 

 the other layers of the mesophyll consist of richly branched 

 cells, whereas in Primula species and Androsaces sept., it is 

 only in the lowest layer that the elements show any stellate 

 ramification. 



Chlorophyll is abundantly present throughout the meso- 

 phyll, and in special cases it was also found in the epidermis. 



As is generally the case with Primulaceae, hydathodes 

 are found at the tip of the leaves as well as on the margin 

 opposite the stronger lateral veins. 



Androsaces sept, has a small group of hydathodes at 

 the tip of the leaves and also on the lower surface of each 

 leaf-tooth; on Dodecatheon frigidum each hydathode is placed 

 on a small, raised, wart-like base. 



