23 



the pith. All plants showed within the limits of the casts smaller 

 pith-cells and cortical cells than normal. 



Myrrhis odorata Scop. 



In structure of stem and formation of cavity, Myrrhis odorata 

 is very similar to Archangelica sativa. 



Four stems none supposed to he hollow had each an upper 

 internode surrounded with gypsum. At the end of 27 days one 

 plant had died, and the others not looking well were cut for exami- 

 nation. In none of them had the stem above the cast grown greatly 

 in thickness. All of them showed the central cavity above and 

 below the cast , and one had so large a cavity within the cast that 

 it is probable that it was there when the cast was applied. A second 

 plant showed within the cast a very narrow but long seam in the 

 middle of the pith, composed of a few cell-remnants crowded together 

 by the surrounding living cells. It is probable that the dead cells 

 in this pith had died after the gypsum was laid around the stem. 

 The 3rd plant showed no cavity within the cast, but a central cylin- 

 der of some size in the pith was composed wholly of dead, uncol- 

 lapsed cells. The outer ring of dead cells had been somewhat 

 crumpled by the pressure of the slightly centrally extending sur- 

 roundig tissue. To one acquainted with the behaviour of the plant, 

 there can be no doubt that the core of cells died after the cast was 

 applied. In all 3 of these plants however the cast was markedly 

 influential in prolonging the life of the pith-cells , since everywhere 

 within the casts there were many more rows of living pith-cells 

 between the bundle-ring and the dead cells at the centre than either 

 above or below the casts. It may be added also that in all cases 

 the living pith within the casts was composed of smaller cells than 

 the living pith beyond the limits of the cast. 



In regard to the conditions of the other tissues within, at the 

 limits and without the casts, it may be said briefly that the same 

 relations existed here in all 3 cases as have been narrated for 

 Archangelica sativa. A description for Myrrhis would be merely a 

 repetition of the one given for that plant. 



