240 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 



elongation of the axis in some instances and the cessation of growth 

 of the etiolated branches was followed by the formation of a number 

 of loose, brownish sheathing scales around the tips of the branches. 

 The etiolated branches of Baccharis did not offer any striking 

 differences in form or size from the normal, although the brief dura- 

 tion of the organs formed in darkness demonstrated that the temper- 

 ature and soil conditions were not suitable for this shrub. Acei-^ 

 ConiHS, Populiis and R/ius developed etiolated branches much 

 longer than those on correspondent normal portions of the shoot. 

 The length of etiolated shoots of Acer was about double that of the 

 normal, an increase that was due in part to the multiplication of the 

 number of internodes, and in part to the excessive elongation of all 

 of these members. The number of etiolated internodes in a branch 

 was about the same as that in juvenile sprouts arising from the bases 

 of trunks, or from calluses on trees in the open, but the lengths of 

 the etiolated internodes was greater than that of the juvenile mem- 

 bers, while the thickness in the two instances were about equal, being 

 greater than that of normal twigs on the shoot or main crown. The 

 approximation of the etiolated and juvenile branches seems to point 

 to the fact that the growth of branches in darkness does not allow 

 development to proceed much beyond the embryonic condition. In 

 one instance the juvenile condition is shown as modified by growth 

 and development in light ; in the other the embryonic stage is con- 

 tinued under the influence of darkness. The endurance of the eti- 

 olated twigs corresponded fairl}' well with the length of an ordinary 

 growing season, but the terminal buds did not continue activity dur- 

 ing the entire period, since most of them soon perished, and lateral 

 buds took up the continuation of the branches. It is notable, how- 

 ever, that none of the etiolated branches succeeded in making such 

 development as to pass into permanent form and to survive after the 

 leaves had perished. Buds of Acer awakened but tardily, and in less 

 number on trees in darkness than in light, and exposure to illumina- 

 tion seems to exercise a stimulative effect on the awakening of the 

 growing points. It was noted that even the occasional exposure to 

 the rays of the electric lamp used in making examinations of the eti- 

 olated specimens produced some reaction in the way of increased 

 development of the buds. The length, diameter, and number and 

 length of internodes of stems of Cornus grown in darkness were 

 much greater than those of normal branches on correspondent por- 



