160 



its surroundings and in this case had been formed by 

 spécial prolifération of the palissade parenchyma, a distinct 

 young meristem immediately below the epiderm. The 

 epiderm cells themselves however, did not take part in the 

 formation of the meristem. 



In a Word, meristem formation may take place as well 

 by cells, descending from the spongy parenchyma and 

 the subpalissade cells, as from such as hâve been formed 

 by hyperplasia of the palissade parenchyma, the epiderm, 

 however, plays no part. In other words : the adventitious buds 

 on the leaves of Gnetum G-nemon are endogenic formations. 



■ In the beginning the young meristem increases in size 

 by its own active growth as well as by new cells from 

 the immédiate vicinity becoming meristematic. 



When the meristem has reached certain dimensions, it 

 partly becomes loose from the surrounding tissue. This is 

 brought about by some of the cells, forming the transition 

 between the meristem and the surrounding tissue, being 

 dissolved and resorbed. (PI. III, flg. 16a, s). 



This dissolution process proceeds along the whole upper 

 side of the meristem, so that the growing point of the 

 adventive bud comes to be placed in a slit-shaped space 

 (PI. m, flg. 17, s). 



The greater the depth at which the meristem was origi- 

 nally formed inside the knob, the thicker is the layer of 

 tissue which ultimately séparâtes the bud from the outer 

 world and the further the development within the enclo- 

 sure proceeds (cf. PL IV, flg. 18 and PI. III, flg. 19). This 

 explains how it is possible that knobs, no larger than 

 1 millimètre, open, while much larger ones remain per- 

 sistenly closed. 



The appearance of two meristems within the same knob 

 is a very common occurrence; once I found as many as 

 four meristems in one knob. 



