Vol. 34 



No. 2 



BULLETIN 



OF THE 



TORREY BOTANICAL CLUB 



FEBRUARY, 1906 



Studies in etiolation 



Augustine Dawson Selby 



t>» 



(WITH PLATES 4 AND 5) 



During the winter of 1902- 1903 the writer carried on certain 

 studies of the effects of etiolation upon several species of plants 

 in the laboratories of the New York Botanical Garden. Most of 

 the species studied were latex -bearing sorts. Owing to the press 

 of regular duties, and to ill health, the publication of the results 

 has been long delayed — far too long, indeed. It seems, how- 

 ever, worth while to present them briefly at this time. An an- 

 nouncement of the results obtained with Persea was made before 

 the Botanical Society of America at its Washington meeting 



January 1, 1903. 



Seedlings of the Alligator pear {Persea gratissimd) were grown 



in a dark room and propagating houses of the Garden, toward the 

 end of 1902. At the end of ten weeks the normal and etiolated 

 plantlets had developed stems approximately equal in length 

 (about 45 centimeters) which consisted of 17 and 19 internodes 

 respectively (plate 4, figure 7). The variation in the length of 

 the internodes of the normal plantlets was slightly greater than 

 with the etiolated. No acceleration was shown in rate of growth 

 by the etiolated plants, nor was the total amount of growth greater 

 than in the normal. The stem-diameters were nearly the same in 

 both cases. All the leaves of the etiolated stems were bract-like 

 and rudimentary (plate 4, figures 3 and 4) ; these did not advance 

 beyond a certain stage of 10 mm. in length, with blades 5 x 2 mm., 

 when they withered and dropped off. These rudiments seem gen- 

 erally comparable with the rudimentary organs b orne on the basal 



J The Bulletin for January 1906 (33 ! 1-66, //. 1-3) was issued 8 F 1906.] 



67 



