MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 245 



ment and differentiation of the tissues of the species of this group 

 reached a much more advanced stage than those of the preceding 

 group, and the period of endurance or existence of the etiolated 

 stems consequent!}^ was as great as in the normal, in many instances. 

 Etiolated stems were distinguished from the normal b}' having less 

 angularity, but no species of this group showed etiolated stems of 

 greater diameter than the normal. 



Species having the largest amount of reserve food stored in the 

 perennial portions of the plant might be expected to be capable of 

 carrying on a relatively greater development of the stem in darkness, 

 or under any conditions in which the plant is forced to rely upon its 

 own supplies or activities. As a matter of fact not all species are 

 capable of carrying on growth and construction to the full value of 

 the food supply. A few species, notably the seedlings of AEsculus 

 exhibit this capacity and doubtless many others might be found ; hence 

 nutrition must be the limiting factor in the development of many 

 species in darkness. On the other hand, the shoots of some species 

 perish, although ample and copious supplies of reserve material remain 

 intact in the storage organs. In such instances it is seen that the 

 difficulty may lie in the difficulty of transporting the food-material 

 to distant parts of an elongating shoot, which customarily construct 

 much of their carbohydrates locally, by means of conduction tissues 

 which are much reduced in cross section and which, in common with 

 other specialized tissues, have failed to reach normal differentiation. 

 In order to give the evidence bearing upon the matter of ability to 

 utilize the entire reserve greater conclusiveness, it would be neces- 

 sary to make a special series of tests in which the requirements of the 

 species when etiolated, as to moisture and temperature would be 

 quite exactly complied with, and the activity of bacterial and fungal 

 organisms upon the storage organs was checked. In so far. as de- 

 fined above therefore, nutrition must be taken as important factor in 

 the divergences of etiolated plants from the normal. It is not clear, 

 however, that nutrition is a major factor in the process, as asserted by 

 Sachs, ^" who said : " Moreover, the size of a plant developed in the 

 dark, as well as the number of roots and leaves formed, are propor- 

 tional chiefliy to the volume and mass of the seed, or better, to the 

 quantity of reserve materials accumulated in it." " At length, how- 

 ever, after a few days, or in the case of very large seeds, after a few 



*"^ Sachs. Physiology of Plants, p. 531. 1887. 



