8 



Thus within the casts nearly all of the « pith » had heen preserved 

 while outside nearly all was dead and collapsed. 



Triticum repens L. 



The rhizome of Triticum repens, which forms a narrow central 

 cavity, presented itself as a favorable object for experiment. None of 

 the many rhizomes examined has shown the presence of a cavity earlier 

 than 6 weeks after the beginning of growth in the spring. In this 

 time the sclerenchyma zone becomes so thick that neither radial nor 

 longitudinal displacement can be thought of as the immediate cause 

 of the death of the cells. In the centre of the rhizome, the cell- 

 membranes, hitherto seemingly strong, become wrinkled and separate, 

 and the collapse of cells forms the cavity. 



Casts were put around young internodes of rhizomes that had 

 reached a length of not more than 3 cm or 4 cm , the stem being exposed 

 by cutting away the sheathing leaves. Thus 4 rhizomes were encased 

 when the internodes had reached less than half the length which the 

 free neighboring internodes subsequently attained. After an interval 

 of 53 days the preparations were examined. One had died, one 

 rhizome had not grown, and two had grown greatly. 



The rhizome that had not grown but was still living, showed a 

 healthy appearance within, the cells being apparently in the condition 

 in which they were when the cast was applied. The 2 rhizomes that 

 had made good growth showed in the internodes within the casts as 

 said above less than i ! 2 the length of neighboring free internodes, 

 and a diameter 10% narrower in one, 25°/ narrower in the other 

 than in the same rhizomes outside of the casts. 



Within the internodes surrounded by gypsum the development 

 of cells was in cross-section normal except that the parenchyma cells 

 were smaller than usual. The mechanical tissue was as well deve- 

 loped in the distal end of the internodes within as outside the casts. 

 Here although the internodes in question were prevented from reach- 

 ing y 2 their normal size , and it is certain that cells not normally 

 extended reached the permanent stage, considering that the growth 

 is intercalary the cells may not have been so very far from their full 

 form when the casts were applied. 



In both these rhizomes that grew well there was a cavity above 

 and below the cast. Within the cast the preparation with the smaller 

 diameter showed no trace of cavity-formation, in the other a cavity 

 was just beginning. 



