J98 



MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 



relation of light to this phase of the activity of the plant. On the 

 contrary the growth of the tissues in darkness occurs, as has been 

 pointed out, as a matter of simple increase of the volume of the tissues 

 without the customary differentiation of the elements, and it is to this 

 unguided action that the epinasty or hyponasty of an etiolated organ 

 is due, which may be different from that of a normal green member. 



Fig. i7v Ervum Letts. A, transverse section of normal stem; B, transverse 

 section of etiolated stem which has been illuminated, showing cortical lacunae. After 

 Ricome. 



In other words the various phases of reaction shown by plants in 

 darkness are not to be ascribed to any direct lack of the stimulating 

 action of light, but rather to the fact that when this stimulating and 

 determinative influence is lacking a most complex and closely corre- 

 lated series of happenings follow, all of which are more or less closely 

 concerned with the primary reaction of growth and increase of vol- 

 ume of various tracts of tissue unaccompanied by the ordinary dif- 

 ferentiations and transformations of tissue ; transformations, which 

 entail not onl}'' the conversion of great quantities of plastic into 

 aplastic matter, the death of large numbers of cells, but also most 

 serious changes in the mechanical qualities of the membranes and 

 the protoplastic enclosures. 



The most serious investigation of the behavior of etiolated plants 

 when illuminated has been carried out by Ricome, but unfortunately 

 his observations seem to have been confined to seedlings. The plants 

 examined were grouped in three classes according to the action of 

 the cotyledons in germination, and the amount of reserve material 

 present. The greater length attained by some species in darkness 



