2l6 



MEMOIRS OF THE NEW YORK BOTANICAI. GARDEN. 



tion to the depth of the water, which seems to be independent of ef- 

 fects of alterations in intensity of illumination. A similar reaction 

 is seen in Uydroc/iaris viof'SJis-ranae when the stature of the petioles 

 of swimming and stranded plants is compared. The elongation of 

 stems submerged below the normal depth is accomplished by an ex- 

 cessive growth of the usual number of internodes rather than by any 

 multiplication of these members in all of the observations which have 

 been brought to the author's attention. '^^ 



Noll has recently proposed that all such such adaptations by 

 which the the length and character of supporting organs are altered 



in order to bring about a better ad- 

 justment with the medium or sub- 

 stratum should be included under 

 the general head of etiolations, 

 which might be distinguished ac- 

 cording to the nature of the cause. 

 Thus the well-known reactions of 

 plants to darkness would be desig- 

 nated as darkncss-ctiolatioiis, while 

 the modifications due to the depth 

 of the water would be water-etio- 

 lations. The same author has also 

 proposed that the specific morpho- 

 genic influence of darkness upon 

 plants should be known as skoto- 

 tomis in antithesis to -phototonus. 

 The former term is acceptable as it suggests a definite term for a 

 phase of reaction on the plant of the plant, which, as previously 

 pointed out by the author, and emphasized by Noll, is not due 

 simply to the absence of the effects of light, but is the reaction to a 

 definite condition. ^^^ 



Rooted aquatics such as Calla ^aliisiris (see page 87) and 

 Peltandra Virginica (see page 144) were found to undergo a slightly 



isspank, A. B. Ueber die Lage und Richtung schvvimmender und submerser 

 Pflanzentheile. Cohn's Beitr. z. Biol. d. Pflanze, i : Hft. 2. 31-86. 1872. 



'•Noll, F. Ueber das Etiolement. Separate a. d. Sitzungsber. d. Nied-Rhein. 

 Gesell. f. Natur- u. Heilkunde z. Bonn. 1901. 



MacDougal, D. T. Critical points in the relations of light to plants. Read 

 before the Society for Plant Physiology and Morphology, Baltimore Meeting, Dec. 28, 

 1900. Abstract in Science, 13 : 252. iqoi. 



Fig. 162. Caulerfa with cylin 

 drical branches formed in darkness 

 Redrawn, after Klemm. 



