15Ô 



possesses three spécimens of Gnetum Gnemon. One of 

 thèse has been continually cultivated in a hothouse where 

 in winter the température was kept at about 25" C. and 

 the air was very damp. The other two were, when I 

 began my investigation, in an other hothouse where the 

 température was lower (in winter on an average 15" C.) 

 and the humidity less O- Whereas of the former I hâve 

 always obtained leaves in différents stages of bud-for- 

 mation, the other two showed the phenomenon only 

 after they had been conveyed to the warmer and damper 

 hothouse. 



Although ail three plants, paying no attention to the 

 formation of adventitious buds, evidently were healthy 

 and did not make a morbid impression at ail, they flowered 

 very rarely. Personally I only observed it with one of the 

 plants from the cooler hothouse. This latter plant pro- 

 duced one single S inflorescence, which enabled me to 

 check the accuracy of the détermination. 



The first external change, noticed with a leave which 

 will form adventitious buds, is that on the tip extremely 

 small yellow dots appear which are seen best when light 

 is falling through the leaf. They remind us in this re- 

 spect of the oil dots in the leaves of the Rutaceae or 

 Hypericum, but as a rule they are bigger and less densely 

 spread than thèse. 



With the bigger ones a hand-magnifler will show that 

 where the dots are, the epiderm of the upper or lower 

 side or of both together is slightly bulged, so that we 

 hâve to do with small vesicles. 



It will be shown presently that thèse vesicles are caused 

 by the sting of a scale-insect Aspidiotus dictyospermi Morg., 

 and as such not restricted at ail to the tip of the leaf. 



1) Thèse two liothouses hâve been deinolished during the récent 

 rebuildings in the Garden. 



