March. 1922. 



SCIENTIFIC AGRICULTURE 



225 



The Influence of Light and of Fluctuating 



Temperatures on the Germination 



of Poa Compressa (L) * 



By .lames \i. Fryer. 

 Department of Field Husbaiulry, University of Alberta. 



The experiments reported in this paper 

 were conducted in October and November 

 1915, but have not been heretofore des- 

 cribed for publication. 



Previous to 1915 the satisfactory germin- 

 ation of seed of Poa compressa (L) in the 

 Canadian Seed Laboratories was more or 

 less uncertain. Samples which from ex- 

 ternal examination appeared to be vital 

 seed, sometimes germinated 10 or 20 per 

 cent. Other similarly appearing samples 

 germinated 50 or 60 per cent. Moreover, 

 the same samples when retested frequently 

 gave results varying widely from the re- 

 sults of the original tests. From general 

 observations it was believed that sunlight 

 and fluctuating temperature conditions 

 were beneficial to the germination of this 

 seed but no definite data had been obtain- 

 ed, and as no literature dealing with the 

 effects of these two factors was available, 

 the writer undertook experiments in Oct- 

 ober 1915, with a view to studying this 

 question to some extent. 



Influence of Sunlight. 



An experiment to study the influence of 

 sunlight on the germination of Canada Blue 

 Grass ma}' first be described. 



From each of twelve samples which had 

 been stored in the Seed Laboratory for at 

 least one year, and which in previous tests 

 had given very low results, two lots of 

 two hundred seeds were indiscriminately 

 counted out, one lot to be germinated in 

 the alternate sunlight and darkness of the 

 natural day, and one in continuous dark- 

 ness, other conditions being identical as 

 nearly as they could be maintained. To 

 ><ecure these conditions an apparatus was 

 devised, a cross section of which is shown 

 in Figure 1, The surface of the soil in this 

 box was marked off by double strips of tin 

 into long narrow areas, each about five- 



eighths of an inch in width. The alternate 

 spaces were covered with hea^y pieces of 

 blue blotting paper as shown, while the re- 

 maining spaces were left uncovered. Lots 

 of seed from the samples were placed on 

 the soil in covered (dark) spaces, while 

 the duplicate lots were placed on the soil 

 in the adjoining uncovered (light) spaces. 

 The ends of the covered spaces were also 

 completeh' darkened. Thus each sample 

 ^^as represented by two tests, side by side, 



11^ / Crozs • Ejection of opparotus used //? 

 mva^ri^ofion of the effect of sunlight 

 on the ^rminotion o/ Poo compressa (L ) 



* This paper is published by permission 

 of the Dominion Seed Commissioner under 

 whose authorization the experiments here 

 reported were conducted. 



one ill alternate light and darkness and 

 the other in continuous darkness. It was 

 thought that the temperature variations in 

 the covered and uncovered spaces could 

 be kept more nearly iDarallel by arranging 

 the spaces in long narrow strips, as by this 

 arrangement heat originating from the 

 sunlight in the light areas would conduct 

 readily to the nearby dark areas, and thus 

 practically parallel temperatures in the 

 two areas would be maintained. 



The box was placed daily in a south 

 window of the laboratory from 9 a.m. till 

 5 p.m. in such a way as to obtain a, max- 

 imum of sunlight. From 5 p.m. till 9 a.m. 

 it was kept in a germinator of the Ham- 

 burg type, the temperature of which ranged 

 from 30 to 35 degrees C. at 5 p,m, to .about 

 25 to 30 degrees C. at 9 a.m. the next day. 

 The soil was kept moist continuously by 

 sprinkling and the temperature of the soil 

 in the box was recorded daily at 9 a,m,, 

 10 a.m., 12 noon and 5 p.m. Some notion 

 of tlie temperature changes to which these 



