238 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 



much reduced size when grown in darkness.'"' It is to be said, how- 

 ever, that the resuhs in question were partly secured by " partial 

 etiolations" and the exact limits of the groups which undergo a re- 

 duction of the bilateral features can not be determined without 

 further investigation. It seems entirely probable that the require- 

 ments of the transpiratory functions might be quite an important 

 factor in a group which has made such sweeping adaptations to the 

 conditions of humidity. 



Etiolation of Xerophytes with Reduced Leaves and Spiny, or Cylin- 

 drical Stems. — The examination of the information obtained by the 

 etiolation of the second group of forms that have made marked 

 adaptations to transpiratory conditions brings in some further con- 

 siderations. Asparagus officinalis (p. 73), Bozvica voliibilis (p. 82), 

 Thcrvillea Sonorae (p. 197), and Eqiiisctum arvensc (p. 103) 

 were cultivated in the dark room under conditions of a higher 

 degree of humidity than that ordinarily, and continuously encoun- 

 tered, by three first-named species. According to the conclusions 

 of Brenner, and the suggestions of Palladine and Wiesner the culture 

 of these plants in a humid atmosphere should have produced a 

 lengthening of the stems and an increase of the surfaces capable of 

 transpiration. It was to be seen, however, that the etiolated stems of 

 this group were in general shorter than those grown in light, the de- 

 crease in length being accompanied by accessions to the thickness. 

 Branching was reduced in all of the species in question when grown 

 in darkness. No extension of the surface was reached by etiolation, 

 or as a result of it, although it is to be said that all of these forms 

 developed stomata, and that the outer membranes were much more 

 adapted to a cuticular exhalation of water than the normal specimens, 

 while the bract-like leaves were actually larger than the normal. 

 The total result could not have been to make an increase of the trans- 

 piratory capacity of the plants examined in any instance, and the 

 conclusion is inevitable that the moisture relations of the individual 

 must play a minor part in the determination of the stature of the shoot 

 when acting simultaneously with the influence of light and darkness, 

 conforming more nearly to the action of CapseUa as outlined by 

 Wiesner.'"** 



I'^Vdchting. Ueber die Bedeutung des Lichtes fiir die Gestaltung blattformiger 

 Kakteen. Jahrb. f. wiss. Bot. 26: 438. Also see Goebel. Organography of Plants, 

 p. 248. 1900. 



^'""Wiesner. J. Formanderungen von Pflanzen bei Cultur im absolut feuchtem 

 Raiime und im Dunkeln. Ber. d. deut. Bot. Ges. 9: 46. 1S91. 



