37 



as to prevent growth except in the roots. (See page 4.) In these 

 cases the bulb remained turgid and growth was almost at a stand- 

 still , while bulbs in normal relations had in the same period fully 

 collapsed and mature leaves had been formed. 



Thus in Juncus for 11 weeks and in Allium for over 4 weeks 

 where extension of organs was made impossible by external resist- 

 ance and all the other normal conditions of growth were present 

 the meristematic tissue had retained its functional capability. 



Several plants of Vicia faba by the use of casts have had the 

 formation of interfascicular cambium in the 2nd and 3rd epicotyle- 

 donary internodes delayed for weeks after it has been formed above 

 and below this position. In 2 such cases the casts were removed 

 without injury to the plant, and within 2 weeks the weak abnormal 

 segments had so grown in thickness as nearly to obliterate the ex- 

 ternal constriction left by the cast. Examination of the internal 

 structure showed that the cambium-zone had been formed and had 

 given rise to secondary elements in the usual way. 



That the cambium itself may be preserved in its functional 

 capability without being allowed to grow may be inferred from the 

 results of de Yries l and Krabbe 2 , the former stating that the mul- 

 tiplication of cells from the cambium proceeds more slowly under 

 pressure, and the latter finding the size and thickness of wall of 

 cambium- cells uninfluenced by pressure, till the pressure becomes so 

 great as to cause all division to cease. 



Three species of plants that have been under experiment have 

 confirmed this point. Casts were applied to internodes of Vicia 

 faba , Dahlia variabilis and llicinus communis subsequently to the 

 completion of the cambium-zone, and the plants so allowed to grow 

 for periods varying from 5 to 6 weeks. Examinations of such plants 

 show that within the given period the cambium produces a ring but 

 3 or 4 cells wide and that this increase takes place soon after the 

 application of the cast. As soon as the intercellular spaces are filled 

 growth is in these plants for the time given practically a at stand- 

 still. On the removal of the casts the cambium resumed its activ- 

 ity and within a few weeks produced as many cells as had 

 been produced in the normal parts of the stem above and below 

 the casts. 



1 De Vries, De l'influence de la pressio-n du liber sur la structure des couches 

 ligneuses annuelles. Extrait des Archives Neerlandaises, T. XI, 1876. 



2 Krabbe, Ueber das Wachsthum des Verdickungsringes und der jungen Holz- 

 zellen. Berlin 18S4. 



