at the time of enclosing them in gypsum has been determined by 

 examining for each case several stems of like development. 



Some objects submitted to experiment have been used for one 

 purpose, some for another ; the peculiar features of each will be found 

 noted with the description under the respective plant species. 



Juncus effusus L. 



Five casts were applied to the bases of stems of Juncus effusus, 

 each cast including several shoots. Some shoots projected above the 

 gypsum, and others were wholly covered. Examinations were made 

 after 4 weeks and again after 1 1 weeks. Those shoots that had pro- 

 jected well out of the gypsum had made farther growth , the cast 

 not preventing elongation. Those that were wholly covered by the 

 gypsum remained during the 1 1 weeks living and almost unchanged 

 The only alteration that could be found in the latter was a growth 

 of peripheral cells toward the centre, forming thus a zone of living 

 cells wider than normal , and crushing the previously existing dead 

 cells together in the centre. 



Allium cepa. 



Several experiments were made by including within a cast the 

 young leaves and the upper part of the bulb of a germinating onion, 

 then securing the cast by cloth and twine bands to the bulb so as 

 to prevent cast and bulb from separating. The longest period that 

 such a cast was allowed to remain was 31 days. 



The results were the same in all the preparations. All parts of 

 the leaves remained alive, the peripheral cells elongating toward the 

 centre and thus filling up the previously existing intercellular spaces 

 there. The bulb itself remained turgid, and on removal of the cast 

 growth was resumed in the same leaves that had for weeks made no 

 enlargement. 



The fact that the spongy parenchyma filling the middle of the 

 very young leaves in Allium cepa is replaced by a large cavity in 

 the mature leaves is familiar to all. Sachs 1 long ago found that when 

 the leaves were grown in darkness they did not become hollow. 



1 Sachs, Ueber den Einfluss des Tageslichtes auf Neubildung und Entfaltung 

 verschiedener Pflanzenorgane. Botanische Zeitung 1863. Beilage. 



