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palisade-cells and i2) they are entirely absent from the "inter- 

 foliar-spaces" li. e. the morphological leaf-stalks). 



As regards the seasonal biology of the leaves it may be 

 observed that at the base of the buds which live over the 

 winter partially expanded leaves usually occur, which probably 

 assimilate for some length of time before beginning their 

 winter-rest; but of course this has not been proved. The buds, 

 moreover, are sharply limited below by dead leaves, which per- 

 sist upon the stems for several years. Bud-scales are absent, 

 and the only protection the younger leaves have is due to the 

 circumstance already mentioned, that they are without stomata 

 exactly upon the small space containing the hydathode which, 

 in the bud-condition, is the most visible and most exposed part 

 of the leaf. 



A specimen from East Greenland (Danmarks 0), collected 

 February 28, 1892, was remarkable with regard to the arrange- 

 ment of its chlorophyll-grains, the latter (in the two upper 

 palisade-layers) having sunk down to the bottom of the cells, 

 of which the upper part was occupied by a large vacuole. The 

 other cells of the mesophyll showed no such feature. Whether 

 this circumstance (which was not observed in any leaf gathered 

 during the period of growth) is really a common winter- 

 phenomenon in S. oppositifoUa in Arctic regions, or is due to 

 the imperfect way in which ordinary spirit-material on the 

 whole is fixed when collected, I am not prepared to state with 

 any certainty. 



I investigated plants of -S. oppositifoUa from the following 

 places: — Upernivik (May 17, 1887), Danmarks (Febr. 18, 

 1892) and Julianehaab (May 22, 1887) in Greenland, Jan Mayen 

 (July 22, 1896), Nova Zembla, Vallanæs (Iceland; Dec. 21, 1893) 

 and from the Botanic Garden in Copenhagen (April 18, 1907). 

 The leaves of all these species agreed very closely in all ana- 

 tomical details. Any difïerence which could be attributed to the 

 influence of the different geographical conditions could not be 



