13 



beginning to unfold, probably then before a cavity was present. The 

 plant in the 4 weeks grew to a length of 6 intemodes showing a 

 weak stem with small leaves. Above the cast was a small swelling. 

 The stem had grown considerably in thickness above the cast, very 

 little below. 



Within the cast a small cavity was present, nearly filled by the 

 pushing of cells. The cortical and pith cells and the bundles were 

 elongated radially. Since the application of the cast, there had been 

 some growth from the cambium in the bundles, and a few cortical 

 cells at the outer end of each bundle began to show thick walls. 



Outside the cast the increase of elements in the bundles was 

 greater than within. The most of the increase in thickness of stem 

 came however from the increase in size of cells. Hence all paren- 

 chyma cells within the cast were smaller than those without. The 

 cortical sclerenchyma above the cast was much thicker-walled than 

 within. Below the cast the thickness of wall was not greater than 

 within, — an abnormal condition. 



x\nother individual whose hypocotyl at a still earlier period of 

 development than the preceding was put into a cast, grew for 38 

 days afterward , but then had a weak development. The external 

 and internal changes caused by the cast were insignificant. A cavity 

 was present within the part in the cast. 



2 . Examination after 48 days. Five plants when the first leaves 

 were beginning to appear between the cotyledons had their hypoco- 

 tyl s encased in gypsum. The longitudinal growth of the stem in 

 the 4 weeks varied between a length of y 3 and 2 / 3 of a meter. 

 Differences within and without the cast varying with the length of 

 stem and leaf- formation were found. In no cases were large 

 swellings present above the cast; 2 of the plants had grown nearly 

 as well as normal ones in the same pot. 



Within the cast all of the plants showed cavities with stretching 

 of cortical and pith cells toward the centre. The weaker plants 

 showed thick-walled cells in the sclerenchyma of the cortex only. The 

 2 stronger plants showed also thick-walled parenchyma cells among 

 the vessels, but only in part of the bundles. The bundles showing 

 these thick-walled cells w r ere the largest and lay opposite broken- 

 down tissue in the cortex. Where the cortex was intact,' the bundles 

 were smaller, weaker and distorted. 



Above the casts the bundles were normal, showing more mechan- 

 ical cells than within ; except in those bundles within which lay 

 opposite the destroyed cells in the cortex. Above the cast the corti- 

 cal sclerenchyma was also stronger than within. 



