MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 295 



amined exhibited negative geotropic reactions, and assumed an up- 

 right attitude at least as to the terminal section. Thus many etiolated 

 stems fell over because of their lack of mechanical rigidity when the 

 apical portions again began to ascend in consequence of the upward 

 curvatures of the tip. This was also true of a large number of bi- 

 lateral and dorsiventral leaves arising from underground stems and 

 rhizomes. Branches were shown in a manner offering evidence 

 of value only in Asparagus and Populus and in both of these in- 

 stances the position seemed to be due directly to apogeotropism, 

 and the angle made with the axial member was often much smaller 

 than in the normal shoot. Leaves arising from aerial shoots in most 

 instances were more nearly upright than in illuminated specimens; 

 in some instances this altered position by which the angle of the 

 petiole with the stem was diminished, might be ascribed to apogeo- 

 tropism, while in the greater majority the position seemed to be due 

 simply to the autotropism of the plant, and the position of the petioles 

 was a matter of the growth of the tissues of the petiole, controlled 

 entirely by the regulatory mechanism of the organism. Coincidently 

 with the assumption of such positions on the part of the axes of the 

 leaves the laminae were generally held in a plane continuous with 

 that of the petiole or but little divergent from it. A number of 

 species including Acer, Cornus and others were examples of a class 

 in which the much reduced leaves were supported in a position quite 

 similar to that of the normal. Polysiichiim acrostichoides is an ex- 

 ample of a leaf in which the position of the terminal portion of the 

 leaf is clearly due to the action of light. 



ILLUMINATIOiN OF ETIOLATED PLANTS. 



The phenomena consequent upon the exposure of an etiolated 

 shoot to light consisting of alterations in position, awakening ac- 

 tivity of dormant organs, and alterations in the methods and rate 

 of growth and development seem capable of interpretation only 

 in the light of the conclusions reached above as to the nature 

 of etiolation. An etiolated sho6t is one in which the length of 

 the main axis, and of the axis of the foliar organs is often much 

 greater than in the normal organs, and the various organs are 



