304 BOTANICAL GAZETTE Iapril 



the rest cut longitudinally, and therefore the 

 ble IV are obviously not for exactly the same sp 

 'he number of changes was insufficient for reliab! 

 it must be remembered that under normal co 



is 



ms 



from tip to base (see also B 3). Certain 



however, are summarized in table V. 



Discussion and conclusion 



Growth. — Region. — So far I have found no reference to the 

 region of growth in the stem of Scirpus. Pfeffer (10) refers to 

 the basal region of growth in the leaves of Canna and Tulipa and 

 in the internodes of grasses, and states that the "length of the zone 

 is always small." He also mentions the careful protection of this 

 zone. The same statements may be made for the zone of growth 

 in the Scirpus stem; the extreme narrowness of the zone, however, 

 is rather surprising. Growth in diameter was not studied. 



Rate. — The results of the experiments were not perfectly har- 

 monious; but in general there seemed to be a tendency toward an 

 increase in rate with a change from air to water, and a decrease 

 with the reverse change. It seems probable, however, that temper- 

 ature was a more important factor than water. 



Diaphragm distance. — From a study of table III it is evident 

 that the variation between culms growing under the same condi- 

 tions was greater than that between culms growing under differ- 

 ent conditions of air and water, thus eliminating water as a direct 

 factor in determining the distance between diaphragms. Its indi- 

 rect effect was studied in experiment 5, and although the data were 

 too scanty for positive statements, certain facts are rather signifi- 

 cant. As there is a normal tendency for the diaphragm distance to 

 increase from tip to base, the cases of increase after a change m 

 environment may not be significant. Two cases of decrease 

 occurred, however; one accompanying a change from high to low 

 temperature, and the other following the reverse change. This 

 would eliminate the temperature change as the direct factor. 

 The fact that both of the cases of decrease in distance were associ- 

 ated with an increased growth rate is the important point. Also, 



