Growth in Eriogonum nudum 



225 



reduction of rate or even shrinkage during the morning, the total amount 

 of growth accompHshed during the hours of dayhght is far in excess for 

 equal periods than that for the hours of darkness (table 2), The ratio 

 of day growth per hour to that of the night was found to be 1.7, 2.6, 

 3.4, 2 and 4 for five different internodes (fig. 8). 



TABLE 2. 



Total growth of various internodes for each day of record (a) and 

 the total growth for the 14 hours of daylight each day, (b) in mm. 

 (Figs. 7, 8). 



Note — The growth record for Ag. 6-8 incl. was not reduced since the part was almost at 

 its limit of growth, the average hourly rate for the whole period being 0.07 mm. 



These ratios are for total net growths merely. As may be seen in 

 table 2, the possible amounts of growth during single hours may in 

 some instances be expressed by a ratio as high as 8 or even 12 (July 

 31st; night rate 0.2, day 2.5) when a part is near its growth limit. 

 Then indeed growth may cease altogether during the night and assume 

 a relatively high rate for a short period during afternoon. 



The comparative rates and amounts of growth on sunny and foggy 

 days are still more pertinent and interesting, since, if direct sunlight is 

 conceived as acting inhibitorily it would seem logical to expect a greater 

 growth on days of high fog, in view of the favourable temperatures which 

 prevail. Table 3 shows that the higher rates for sunny days are fre- 

 quently higher than for foggy days — one hour-rate (that of August 24th, 

 15 hour) being very exceptional and notably higher than any others. 

 Since however the rates on sunny days fall so late, it is evidently 



