DIAPHRAGMS OF WATER PLANTS 



II. EFFECT OF CERTAIN FACTORS UPON DEVELOPMENT OF 



AIR CHAMBERS AND DIAPHRAGMS 



Laetitia M. Snow 



(with three figures) 



The experiments reported in this paper were started at Wellesley 

 College in 1914-1915, and were continued at the University of 

 Chicago during the winter of 1915-1916, It was intended to 

 repeat the experiments and confirm the results, but as it has been 

 impossible to do so, it seems better to report the work in its present 

 incomplete condition than to delay its publication any longer. 

 Thanks are due the Association of Collegiate Alumnae for the 

 grant of the Alice Freeman Palmer Memorial Fellowship for 191 5- 

 1916, the Missouri Botanical Garden for the material of Scirpus 

 validus which was collected and started at St. Louis, and the 

 botanical staff of the University of Chicago for their cordial co- 

 operation in placing the facilities of the laboratory at my disposal. 



Water 



As the general impression is that an increase in the water con- 

 tent of the soil produces an increase in the amount of air-containing 

 tissue, culms of Scirpus validus were allowed to grow alternately 

 under water and in the air, in order to note the effect of the change 

 upon the air spaces and diaphragms. 



Experiment i 



In order to be sure that the part studied actually grew under 

 the desired condition, it was necessary to ascertain the region of 

 growth of the stem. Consequently in 1914-1915 culms were 

 marked in 2 mm. sections from the tip downward. In some cases 

 the marks extended to the sheathing scale leaves at the base 

 (called "to sheath" in table I); in others the sheath was stripped 

 off and the marks carried down the stem to the rhizome (called 

 culm" in the table). DD 5 showed a discrepancy between the 



297] [Botanical Gazette, vol. 69 



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