MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 25 1 



process in Hicoria and other species. The difference in diameter 

 between the base of an etiolated stem and the portion a few centi- 

 meters above it is often very great comparatively. 



Bast Fibers of Etiolated Stems. — The extended periods over 

 which the plants used in my own experimental tests were observed 

 gave much better opportunity for the examination of the behavior of 

 the bast fibers than have been enjoyed by any previous worker that 

 has dealt with this subject. The differentiation of this tissue was but 

 slight in Apios, Acer, AEsctilus, Aster, Castanea, Cornus, Fagus^ 

 Falcata, Lysimachia, Menisperimnn, Populiis and ^lercus, and but 

 little thickening occurred in the walls, although some of the species 

 in this group develop stems in darkness that continue growth for 

 several months. On the other hand, the species of Hicoria that 

 were cultivated in the dark room carried the development of the bast 

 fibers to an advanced stage, although corresponding to Castanea and 

 ^cercus in the general activit}^ of the cortex, epidermis and phel- 

 logen. So far as other features are concerned, a general inspection 

 of the structure of the etiolated stem of Hicoria and ^lercus does 

 not show that the woody tissues of the former are carried beyond 

 those of ^lercus. Development and differentiation of the bast fibers 

 may be carried on in etiolated stems, but as stated above it occurs in 

 but few species. 



Endoderm, Pericycle, Sieve Tissue, Cambium and Generative 

 Layers of Etiolated Stems. — The numerous questions connected 

 with the origin and occurrence of the endoderm and pericycle made 

 it impossible to carry out a critical study of these formations in the 

 time at the disposal of the author, and but little study was made of 

 the sieve cells in the various stems. The last-named tissue seemed 

 to be differentiated but slightly in most of the etiolated stems, so far 

 as the records at hand may be relied upon. The following striking 

 facts concerning the activity of generative tissues may be cited at this 

 place. A distinct cambium is not normally formed in Apios, the 

 stem soon ceasing to increase in thickness in light. Etiolated stems 

 however show a diameter greater than the normal, and a generative 

 layer arises in the customary position of the cambium, while a second 

 is formed in the pericyclic region, which is about half the thickness 

 of the primary generative layer. A marked cambium was present 

 in etiolated stems of Castanea, Fagns, Hicoria and ^lercus. 

 Phytolacca formed the first of the secondary layers of cambmm 



