The young shoots of E. limosum when 5 cm or 6 cm above the 

 earth will show only the central canal and those in the bundles ; 

 the intercarinal canals have not been formed. The latter are how- 

 ever at this time present in the stalk at the level of the earth or 

 just below and progress gradually upward, the nearness of the ap- 

 proach to the apex being exceedingly variable. Some stems may have 

 no intercarinal canals from the apex down through the distance of 

 a dozen internodes. 



Five shoots not more than 5 cm in height were enclosed in gypsum 

 to within a short distance of the growing point. 21 days afterward 

 when the stems had reached a height of 20 cm , 2 of them were sec- 

 tioned. The growth in thickness outside of the cast had been slight, 

 but the casts had prevented the internodes which they inclosed from 

 elongating. One plant showed living cells in the place of intercarinal 

 canals within the cast while such canals were present above and 

 below, and the other plant which was a strong one showed inter- 

 carinal canals smaller within the cast than above and below. 



Forty-four days after the casts were applied the other three plants 

 were examined. They had grown to a height of about 40 cm without 

 growing much in thickness. All of them showed intercarinal canals 

 present within the limits of the casts. Moreover structural differ- 

 ences within and outside the casts were not to be seen. In such 

 a stem where there is so much free space internally, where there has 

 been scarcely any growth in thickness, and where the longitudinal 

 elongation would have been small, there cannot have been much 

 unusual pressure called forth. 



Petiole of Ricinus communis L. 



The petiole of Ricinus communis becomes hollow before elongation 

 is complete, the schizogenous beginning of the cavity being soon 

 followed by the collapse of cells. 



Parts of 2 petioles before any dead cells or cavity were present 

 were enclosed in gypsum. One grew subsequently for 26 days, the 

 other for 45 days before being cut for examination. The changes 

 were alike in both. Within the casts one had in the cross-section 

 3 or 4 dead cells at the centre, the other 10 dead cells; but neither 

 had a cavity. The multiplication of elements in the bundles had 

 been about half within the casts what it was outside, and the thicken- 

 ing of cell- walls in phloem, xylem and at the inner ends of the 

 bundles was less than in normal parts of the same leaf-stalks. 



