2 2 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 



duplicated by no other worker on this subject so far as the records 

 are available. 



Klein ^' made a series of experiments to determine the factors to 

 which the nocturnal spore formation of Botrytis cinerea might be 

 ascribed, and concluded that the blue violet rays exerted such direct 

 action as to prevent their production during the daytime. The red- 

 yellow rays facilitated spore formation, and the absence of light 

 allowed it to proceed normally. 



The etiolation of a number of such extremely hairy forms as 

 Urtictila ptlultfera^ Cynoglosswn officinale^ Anchusa officinalis, Cu- 

 curbita Melopepo, Ecballiuni elaterium, Soja hisjyida, Salvia argen- 

 tea, Stachys lanata, Mirabilis Jalafa, Abutilon Avicennae, Gloxinia 

 hybrida, Solanuni tuberosum, Dahlia variabilis, Mentha piperita 

 and M. crispa, by Schober " resulted only in the diminution of the 

 size of the trichomes, or excessive growth correspondent to that of 

 the organs on which the}' are borne. The stellate hairs of AbtUilon 

 were not borne by etiolated specimens. The above results must be ac- 

 cepted with some caution, however, since etiolations were affected by 

 covering shoots with flower pots and could hardly have been absolute. 



As a result of some researches upon the structure of leaves 

 Dufour ^^ concluded that these organs reached a greater extension in 

 sunlight than in shade, that the epidermal cells were larger, the 

 number of stomata greater and that a continued formation of these 

 organs ensued occurred through a large part of the period of develop- 

 ment of the leaf. Stahl" had previously published the results of his 

 extensive researches upon the general relations of the form and size 

 of leaves to light exposure and other factors. 



Uhlitzsch^" showed that the extension of petioles is greater in 

 etiolated than normal leaves, but that growth may be variously 

 affected by light in different species. The length of the period of 

 growth is also dependent upon the intensity of the illumination. 



"Klein, L. Ueber die Ursachen der ausschliesslich niichtlichen Sporenbildung 

 von Botrytis cinerea. Bot. Zeitung, 43 : 6. 1885. 



"Schober, A. Ueber das Wachstum der Pflanzenhaare an etiolirten Blatt- und 

 Achsenorganen. Zeitschr. f. Naturw. IV. 58 : 4 : 556. Abstract in Bot. Centralb. 28 : 

 39. 1886. 



■'^Dufour, L. Influence de la lumiere sur la structure desfeuilles. Bull. Bot. Soc. 

 d. France, II. 8: 92. 1S86. 



" Stahl, E. Ueber die Einfluss des Standortes auf die Ausbildung der Laubblatter, 

 18S3. 



'eUhlitzsch, P. G. Untersuchungen liber das Wachstiuii der Blattstiele. 1887. 



