144 IIIK PLANT WORLD 



a thorough irrigation. Up to this time there had been very 

 little spring rain and the shallow soil was parched dry. 

 The accompanying table shows no more increase of growth 

 on the days following than the usual daily variations would 

 account for. The other plant was irrigated on April 41th. 

 From April 8th to 14th, the elongation of the shoot was 

 3 feet, 3 in. Ah average of 6}'j in daily. From April 

 14th to April 1 8th, the increment was 2^; in., or a daily aver- 

 age of 6j4- if^- It should be noted that this was while the 

 leaves were still turgid and probably the growing portion of 

 the shoot was supplied with sufficient water for the maximum 

 growth. Later as the leaves were wilting, and the reserve 

 supply diminished, a different result might be obtained, 

 though it may be added that it Is a matter of common obser- 

 vation in this region, for agaves to bloom and fruit normally 

 in soil so dry that the stored water is the only possible avail- 

 able supply. 



After the stalk had ceased elongation, and when many 

 of the leaves were only partially wilted, (others quite dried 

 up) the dry soil was again irrigated. No appreciable growth 

 (in length) of the stalk resulted, and no increase in the tur- 

 gidity of the leaves could be noticed. 



Regarding the age of these plants, the larger one was set 

 out as a two year old rosette in 1894, the other a few years 

 later, but just when is not known. 



Measurements were started on April 8th, 1908, and con- 

 tinued ciaily until June 2nd, when growth had practically 

 ceased. Owing to the difficulties in measuring, an error of at 

 least half an inch was unavoidable. This may effect the 

 record for any one ciay, but the average rate for a series of 

 days would not be prejudiced. 



The following table shows the daily growth from April 

 8th to June 2nd. After that the growth was too slow for 

 measurement, being 3 in. in 13 days. After June 15th, no 



