406 The American Naturalist. [May, 



interesting pieces of evidence is that brought forward by M. Gaston 

 Bonnier in a long article, — Influence de la lumiere electrique continue 

 sur la forme et la structure des plantes,— running through four num- 

 bers (78, 79, 80 and 82) of the Revue generate de Botanique, Paris, 

 1895. In a previous study (Les plantes arctiques comparees aux 

 m£mes especes des Alpes et des Pyrenees, Rev. generale, VI, 1894, p. 

 505) M. Bonnier had shown that arctic plants differ noticeably from 

 the same species growing in alpine regions, e. g., in the greater thick- 

 ness and simpler structure of the leaves, and had attributed this to the 

 feebler light of the arctic region and to the greater degree of moisture. 

 By means of feeble electric lighting and a moist cool temperature he 

 has now been able to produce these differences synthetically in Paris, 

 i. e., to take alpine plants and convert them into arctic ones. He has 

 also shown by experiments on a great many plants, details of which are 

 given, that feeble continuous electric lighting for a period of six months 

 causes decided histological and morphological changes in nearly all 

 of them, except such as grow in the water. Many plates are given in 

 connection with this paper showing morphology and histology of nor- 

 mally grown and continuously lighted plants and the changes in the 

 structure of the latter are frequently so great that no one would believe 

 the sections to have been derived from the same species. About 75 

 species were experimented on and these belonged to many different 

 families. The structural changes obtained in Helleborus niger, Fagus 

 xilmtica, Finn* fiu*trinc<i, Pice>i < ■■ ■ are particu- 



larly striking. To illustrate, in the needles of Pinus the characteristic 

 arms or folds of the cortical parenchyma disappear entirely and there 

 are several other equally striking changes. In Pteris the petiolule 

 under the influence of the continuous electric light takes on an epider- 

 mis which is clearly distinct from the subjacent cells, and the cells of 

 which are elongated perpendicularly to the surface of the petiole and 

 are much larger than the neighboring layers of cortical tissue while 

 their walls are not thickened ; the cell layers immediately under the 

 epidermis (sclerenchymatic tissue) do not become thick-walled and are 

 rich in chlorophyll ; the intercellular spaces in the cortical parenchyma 

 have wholly disappeared ; and, finally, there is no endodermis, although 

 it is well developed in the normally lighted plant. The palisade tissue 

 was imperfectly formed in bright electric light and in many cases en- 

 tirely disappeared in feeble electric light thus confirming what has been 

 believed for some time on other grounds, namely that the development 

 of the palisade tissue of leaves stands in direct relation to the intensity 

 of the light. Additional experiments seemed to indicate that most of 



