1896.] Vegetable Physiology. 407 



the results obtained were due not to the kind of light but to the grade 

 of intensity. The whole paper will repay careful perusal. The author's 

 main conclusions are given in the following paragraphs, as nearly as 

 possible in his own phraseology: Modifications due to continuous 

 electric light. The organs completely developed in continuous light 

 have the following characters : (1 ) The chlorophyll is more abundant 

 and is more uniformly distributed in all the cells which contain it 

 under normal lighting. Moreover, chlorophyll grains may appear even 

 in elements which do not contain them in a normal state, in the bark 

 clear to the endodermis, or even in the medullary rays, in the pith, 

 sometimes even to the central cells of the pith. (2) The structure of 

 the blade of the leaf is simplified ; the palisade tissue is less distinct or 

 disappears entirely, the epidermis has cells with thinner walls, and the 

 cortical cells lose their special differentiations (transformation into 

 sclerenchyma of the petioles of the fern, reduplication of the membrane 

 of the cortical cells of the needles of the pine, etc.). (3) The struct- 

 ure of the stem is simplified; the bark is less clearly divided into two 

 different zones or even has all its elements alike; the cork is tardy or 

 but little developed, the endodermis is less well defined, or is no longer 

 distincl from the neighboring cells; the cortical tissue, the tissue of the 

 medullary rays, and that of the pith are composed of elements which 

 more nearly resemble each other ; the sclerification and the lignifica- 

 tion of the pericycle or of the wood fibres is diminished or disappears 

 entirely ; the interior calibre of the vessels is often greater ; the peri- 

 medullary zone and the libre are less differentiated. 



It may be added that the structure in discontinuous electric light 

 approaches more nearly the structure in normal light than that in the 

 continuous electric light. Finally, it should be noted that this latter is 

 intermediate between the normal structure and that in obscurity, 

 except the greening. The simplification of structure under continuous 

 feeble electric lighting is, therefore, to be ascribed partly to the contin- 

 uity of the light and partly to its feebleness. To sum up, a sort of 

 ijrcpn etiolation is produced by continuous electric lighting, for the two 

 principal characteristics of the changes obtained are the superabundance 

 of chlorophyll and the simplification of the structure. 



Somewhat similar results may be obtained by growing plants for some 

 time in weak daylight in the middle of a room and then comparing 

 their structure with that of the same species cultivated in the bright 

 light of a window. Modifications of form and cell structure are still 

 more pronounced if the same plants are grown in total darkness. 

 Anatomical characters are sometimes used in classification and M. 



