118 CLARK— ON WATER CONTENT 



At the end of each day's work, a paste board box containing the 

 various envelopes with their leaves was placed in the warming oven. 

 No constant temperature could be maintained here. A wood fire was 

 made up 3 times daily for getting meals, and often, depending upon 

 household needs, it was kept burning for the greater part of the day. 

 At its hottest, the oven registered 118° F. After a week the leaves were 

 taken from the oven, removed from their respective envelopes, and 

 weighed. From the fresh and dry weights, the water content, based 

 upon the fresh weight, was calculated. (See p. 112.) 



For transpiration tests, attached twig ends were bent about a foot 

 from the tip into a pint cup filled with water. Since wetting of leaves, 

 according to Haberlandt,*' Wiesner,^ and Burgerstein,* hastens tran- 

 spiration rate, great care was taken that the leaves did not come in con- 

 tact with the water. Following the method of De Vries,^ the twigs 

 were cut off under water, and then without permitting air to come in 

 contact with the cut surface, they were transferred to homeopathic 

 vials containing water. 



The vials were about three-fourths full of water, and a cork was made 

 by wrapping cotton closely around the stem of the twig and pushing it 

 tightly into the mouth of the bottle. The cotton cork was covered 

 with a thick layer of vaseHne to exclude all air, and the vaseline was 

 covered with a thin layer of cotton to prevent the leaves above from 

 coming in contact with the vaseline. Normal transpiration would have 

 been interfered with had the leaf surface received a coat of vaseline. 



These experiments were prepared by 7 a. m. and the vials containing 

 the twigs were placed always in the same order in the same shallow 

 wooden box, which was kept always in the same position on top of the 

 oil-cloth, covering the above mentioned dry-goods box. Thus placed, 

 the twigs were left for an hour to overcome the shock of separation from 

 the tree and to become adjusted to new conditions. 



* Haherlandt, F. Das Austrocknen abgeschnittener und benetzter, sowie abge- 

 schnittener und nicht benetzter griiner Blatter und Pflanzenteile. (Wissensch. prakt. 

 Unters, auf dam Gebiete des Pflanzenbaues, herausg. von Fr. Haberlandt, Bd. II, 

 Wien 1877, p. 130.) 



' Wiesner. Studien iiber das Welken von Bliiten und Laubsprossen. Ein 

 Beitrag zur Lehre von der Wasseraufnahme, Saftleitung und Transpiration der Pflan- 

 zen. (Ebenda, Bd. LXXXVI, 1882, p. 209.) 



* Burgerslein, Die Transpiration der Pflanzen, 1904, p. 68. 



' De Yries. Uber das Welken abgeschnittener Sposse. (Arb. d. Botan. Inst. 

 Wurzburg, Bd. I, Leipzig 1874, p. 287.) Burgerstein. Die Transpiration der 

 Pflanzen, 1904, p. 73. 



