296 MEMOIRS OF THE NEW YORK BOTANICAI. GARDEN. 



held in positions much different from those customary in the sev- 

 eral species, while the bulk of the stems and leaves is composed 

 of a mass of cells very imperfectly, or scarcely at all differen- 

 tiated toward their final form, and Hut little adapted to the performance 

 of the normal functions, being in a much more embryonic condition. 

 Whatever development may be incited in such plants takes place 

 under extraordinary conditions. The amount of tissue present in 

 which differentiation might ensue is much greater than the ordinary 

 because growth has taken place without morphologic changes ensu- 

 ing in an equal manner. Again, the leaves and other organs are in 

 a position divergent from the normal, and their assumption of the 

 normal attitude is to be made by a mechanism consisting of tissues 

 not made up in the same manner as the normal. 



Illustration of the action of a monocotyledonous species with 

 netted venation of the leaves is afforded by the observations on 

 Artsaema triphylluni (Fig. 14, and also p. 60). Here the etiolated 

 petioles and scapes have reached a length beyond the normal before 

 being illuminated, and this stature appears in the final position of the 

 plant after illumination. Futhermore, the form and position of the 

 folioles are different from the normal and they do not reach the full 

 expansion. The most marked deviations from the normal are 

 offered by the spathes. These organs are more slender than the 

 normal when etiolated and the normally over-arching hood is held in 

 a position approximately upright, that is in continuation of the plane 

 of the lower portion of the spathe. Exposure of such etiolated 

 spathes to light resulted in every instance in such excessive growth 

 of the tissues of the inner surface that the hoods were curved out- 

 wardly until a position nearly horizontal was reached with the inner 

 •surface uppermost. 



The illumination of etiolated specimens of Asplenimn ^laty neuron 

 (p. 78 and Fig. 31) resulted in the development of the pinnae, and 

 in the assumption of a recumbent position of the leaves. Etiolated 

 leaves of Peltandra Virginica (p. 147, Fig. 102) showed some further 

 elongation of the petioles after exposure to diffuse daylight, but the 

 most striking feature consisted in the reactions of the laminae, which 

 moved from the upright etiolated position to one approximately hori- 

 zontal. During this process the laminae which were below the 

 normal size expanded so irregularly that one of the basal lobes 

 reached a size two or three times as long as the other giving the leaf 



