196 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 



etiolated branches are thus seen to be excessively elongated, a fact 

 accounting for the superior length of these members. 



The normal stem of the current season's growth showed a col- 

 lapsing epidermis, an underlying collenchymatous layer of cortex, 

 and an inner cortex with larger elements and thinner walls. Both 

 regions contained chloroplasts. The bast fibers of the pericyclic 

 region were grouped in such manner as to give the usual crescentic 

 transverse section, being separated by the external continuation of 

 the rays, which also separate the bundles widely. Some reddish 

 coloring matter in the outer layer of the cortex was almost masked 

 by the brownish tinge of the walls of the epidermis. 



Etiolated stems showed structural divergences of 

 degree only. The phellogen, collenchymatous layer 

 and inner cortex were distinguishable. The cortical 

 cells were furnished with thinner walls and contained 

 so much reddish coloring matter that the etiolated 

 stems had a decided pinkish tinge. The bast fibers, 

 which are grouped in about twenty clusters in the 

 normal, appeared in about forty smaller groups in 

 etiolated stems, the crescentic outline of the trans- 

 verse section appearing more flattened. The cause 

 of this apparent multiplication of the clusters of bast 

 fibers is not clear. It might be ascribed to the non- 

 FiG it;2 Branch development of some of the fibers, thus breaking the 

 of Fag-tis Ameri- normal clusters into smaller groups, the elements hav- 



cana^ which has j^g thinner walls than in the normal. Cambium was 

 been in darkroom , . ,• 1 . 1 , 1^1 in 



o ^, . present m etiolated stems and the medullary rays were 



o months. -4, nor- ^ J J 



malbudwhichhas not SO wide as in the normal. Less thickening oc- 

 notawakened; ^, curred in all of the woody tissues. Stomata were 

 ' ^,*^'° ^*^. " ^ present on the dorsal (lower) surfaces of the etiolated 



on short etiolated * \ . 



branches. leaves, although nothing but the most minute open- 



ing could be detected between the guard cells. 

 Bonnier'^^ cultivated Fagus sylvatica in continuous illumination in 

 the same manner as ^^5cw/?^5 (see page 191), and found that phellogen 

 was not formed under such treatment. The number of sieve tubes 

 was less than in the normal, and the rows of vessels and tracheids 

 were seen to be more closely crowded together by the inferior 



'''Bonnier, G. Influence de la lumiere electrique continue sur la forme et la struc- 

 ture des plantes. Rev. Gen. d. Bot. 7: 300. 1895. 



