MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 207 



dition uniformly favorable to the growth of certain organs and 

 tissues, that the aspect of plants grown in uninterrupted illumi- 

 nation must be ascribed rather than to any green " etiolative " 

 effect supposed to be produced. Thus in continuous exposure to 

 illumination by Bonnier, a much greater development of chloro- 

 plasts and formation of chlorophyl ensued than in the normal ; the 

 bark, and practically all of the parenchymatous tissues containing 

 chlorophyl even to the central pith. The tissues of the leaf did not 

 reach the extreme stages of differentiation characteristic of normally 

 exposed organs and the same may be said of the stem in which the 

 parenchymatous tissues showed but little differentiation ; bark was not 

 developed, and endoderm was not always distinguishable. In the 

 case of the hellebore special alterations ir the development of the 

 endoderm and pericycle were noted. Because of the general arrest 

 of the morphological development of the stem, which in the very na- 

 ture of the plant must be similar in some respects to those resulting 

 from etiolation, or any other cause retarding development, it may 

 not be concluded that the two processes are similar. So far as the 

 results of Bonnier may be interpreted, the exposure to the illumina- 

 tion in question showed no especial feature due to the continuity of 

 the illumination, but may rather be ascribed to the accentuated effects 

 of an illumination of low intensity. 



Schiibeler '^^ transported a number of cultivated and native species 

 from lower latitudes to places in the northern part of Scandinavian 

 peninsula where they would be subjected to a continuous illumina- 

 tion during a period of two months, during which the sun remains 

 above the horizon in that locality. It is to be noted that the intensity 

 of such illumination is far below that of temperate and tropical local- 

 ities. The vegetative period of such species was notably shortened, 

 and the seeds produced were larger than the average. The effect 

 of such continuous illumination was to cause an accumulation or 

 increase in the amount of certain aromatic and flavoring substances, 

 and to increase the amount of coloring matter in leaves and 

 flowers, while diminishing the amount of saccharine matter present. 

 A specimen of Acacia lophantha did not show any of the usual 



^^^ Schiibeler. The effects of uninterrupted sunlight on plants. Abstract in Na- 

 ture, 21 : 311. 1880. 



