76 



SCIENTIFIC 



Aug. lltli tlircc inches 31.707 



half length 30,647 



full length 30.477 



full length with roots. 31.368 



Aug. 13th three inches 31.707 



half length 31,265 



full length 31.242 



full length with roots. 31.376 



Aug. loth three inches 31.956 



half length 30.352 



" . " full length 32.167 



full length with roots. 31.458 



The above figures show a good deal of fluctuation 

 which must be attributed to experimental error; yet, 

 when the average results are taken, they are found to 

 he fairly regular and satisfactory. The average weight 

 of 1000 kernels for the whole period from each length 

 of straw is as follows: 



three inches 23.034 grammes 



half length (about 20 inches).. .. 22.918 



full length 23.032 



full length with roots 23.254 



It is at first rather surprising to lujte that the heads 

 which were gathered with only three inches of straw 

 gave kernels fully as large as those with half length 

 or full length of straw. They are. however, somewhat 

 smaller than those obtained from the full length of 

 straw with part of the roots attached. These 

 facts can be easily explained. Under the conditions 

 of the experiment, tlie drying of the straw would be 

 very rapid and would allow scarcely any time for the 

 t rausfer of material from the straw to the grain. With 

 some of the roots attached, however, more moisture 

 wotdd be pi-esent and the period of activity after the 

 harvesting M^ould be longer. It is clear that when the 

 drying process is very rapid, it is immaterial how much 

 of the straw is retained. 



An interesting observation on the ease with Avhich 

 the heads could be threshed was made during the study 

 of this material. Quite often there was a noticeable 

 diffei'cnce in the ease of threshing between the heads 

 with only three inches of straw and those having the 

 full length of straw with the roots. In some cases the 

 differences were more marked than in others. 

 Tbese facts can be explained in the same way as 

 we explained the greater weight of kernel ol)tained 

 from the heads with roots attached, namely, that the 

 jn-esence of the roots allowed a longer and therefore 

 more thorough ripening to take place. As is well 

 known, the riper the head, the easier it is to thresh. 

 The heads which were gathered even as late as August 

 11th with only three inches of straw attached proved 

 very hard to thresh. 



In studying the irregularities of the results, one must 

 not be too quick to suppose that they are always to be 

 accounted for by experimental errors, because it must 

 be remembered that the daily temperatures throughout 

 this i)eriod fluctuated considerably. Obviously, the 

 development of the kernel is more rapid at high tem- 

 peratures, provided they be not fatally high, than under 

 cooler conditions. During the progress of the exi)eri- 

 ment, the mean daily temperatures at Ottawa (the 

 average between the maximum and minimum) varied 

 from 65.9 degrees Fahrenheit on July 28th (and 

 August 4th) to 84.8 degrees on August 1st. 



The grain was cut finally on August 15th. It had 



!^ G R I C U L T U R E February, 1921 . 



then reached the proper degree of maturity for ordin- 

 ary harvesting in eastern Canada, where it is often 

 customary to allow the grain to stand in the field a 

 good deal longer than is usually the case on the Central 

 Plains. 



Inasmuch as the differences noted between the 

 weight of the kernels from the heads with only very 

 short straw and those with long straw and roots were 

 so very slight, we shall do better to consider the whole 

 crop gathered on each date as a unit, thereby dealing 

 with a larger number of seeds and reducing the expe- 

 rimental error. The average weight of 1000 kernels 

 for each date of cutting is as follows: 



July 21st 4.545 grammes 



" 24th 8.452 



• 27th 13.758 



■• 30th 19.427 



Aug. 2nd 25.184 



4th 27.543 



6th 29.846 



8th 30.968 



■ nth 31.050 



" 13th 31.398 



•• 15th 31.483 



These figures form an almost perfect series which 

 would certainly have been even more nearly perfect 

 had there been no fluctuations in the mean daily temp- 

 eratures. These results arc very striking when plotted 

 in the form of a rough curve. The.v show that from 

 July 21st to about August 2ud the rate of increase in 

 the weight of 1,000 kernels was very rapid and fairly 

 constant, in spite of the cool weather which occurred 

 on July 28th and 29th. The rate of increase in weight 

 fell off after the very hot days August 1st and 2nd, and 

 became .sh)wer and slower during the relatively cool 

 weather which extended to the end of the experiment. 

 There is a slight bend in the curve on the 4th of August 

 which corresponds exactly with the low temperatures 

 of August 3rd, 4th and 5th. When we consider the 

 luidoubted effect of temperature, we are quite justified 

 in altering our curve slightly in accordance with the 

 weather. Obviously a hot day will be one of abnormal 

 activity and a cool day will show a slowing up of phy- 

 siological processes. After making the slight alter- 

 ations for abnormal weather the curve becomes extrem- 

 ely regular. (See the broken line on the chart.) 



The writer also approached this matter from another 

 jioint of view and has determined (as well as the 

 available details allow) the dailv gain in weight of 

 1000 kernels. 



Gain in weight of 1000 kernels. 

 July 22nd, 23rd, and 24tli. . 1.302 grammes per da,v 

 •• 25th, 26th. and 27th.. 1.769 

 •• 28th, 29th, and 30th.. 1.890 

 •• 31st, Aug. 1st and 2nd. 1.919 



Aug. 3rd, and 4th 1.180 ■■ •• " 



5th, and 6th 1.152 ■■ •■ " 



7th, and 8th 561 •' •• " 



9th. 10th and lltli. . . .027 



" 12th and 13th 174 " " " 



•■ 14th aud 15th 043 " " " 



In jilotting the above figures each observed point has 

 to represent two or three da.vs. It is therefore placed 

 in the middle of the period. The solid line connects 

 these determinations. 



The following are the mean daily temperatures ob- 



