MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 235 



lation that exists between the rate of growth of the root and shoot, 

 but so far as his data may be taken to bear upon this question in 

 hand, the total amount of growth in etiolated roots was less than in 

 the normal. 



C. Kraus'"'' records his observations that the roots of etiolated 

 plants do not reach the stature of normally cultivated plants, which 

 he supposed was a direct correlation with the increased length of the 

 shoot. 



It appears as a consensus of the evidence upon this point that the 

 root-systems of seedlings do not attain normal development when the 

 shoot is fully etiolated. The numerous difficulties in the way of 

 making accurate measurements have prevented the acquisition of 

 data concerning the roots of adult perennial plants confined in the 

 dark chamber during a vegetative season. The theories which at- 

 tempt the explanation of this lessened development as a correlation 

 with the increased length of the shoot have been found untenable 

 from the fact that the length of the roots and shoot do not vary con- 

 versely as proven by Strehl. The supposition of Detmer that the 

 lesser total length of the roots was due to the lack of material usually 

 furnished by leaves is also quite beside the point, since this relatively 

 diminished growth of the roots ensues when an ample supply of re- 

 serve material is present in the hypocotyls or endosperm from which 

 it might readily be conveyed to the roots, and with much less ex- 

 penditure of energy than from the leaves. The only causes which 

 might affect the development of the root-system would be the use of 

 water by the shoot and the demand for anchoring power or mechan- 

 ical rigidity because of the strains exerted by the weight of a bend- 

 ing shoot. Etiolated shoots are erect, for the most part, and when 

 disturbed easily and readily fall over, the roots being wholly inade- 

 quate to hold the shoots in position. It is well known, however, 

 that the branching and growth of the root is quickly influenced by 

 the conditions of absorption and transpiration affecting the shoot, 

 and this feature is the only one which may be offered to account for 

 the lessened development of the root-systems of etiolated plants, espe- 

 cially seedlings. 



Effect of Darkness upon Succulents. — On account of the peculiar 

 relations borne by the leaves of succulents to the stem it will be most 



'^^Kraus, C. Ueber einige Beziehungen des Lichtes zur Form- iind Stoffbildung 

 derPflanzen. Flora, 61 : 145. 1S7S. 



