F. KiDD AND 0. West 7 



tures of r-2° C, 5°-6° C, 12° C, and 24° C. respectively. When 

 germination was complete {i.e. when the cotyledon had attained a length 

 of from 2 to 2-5 cms.) the seedUngs were rinsed with water to remove 

 sand, and the 20 most vigorous were forthwith planted ont in four 

 large flower-pots filled with good compost. After one day, during 

 which they were kept in the shade, these flower-pots were sunk in the 

 ground in a part of the Botanic Gardens where uniform illumination 

 was assured, and from the time of germination onwards the plants were 

 grown under similar external conditions. 



Curves A and B in Fig. 1 give the temperatures obtaining at 1 p.m. 

 and at 7 a.m. respectively from March 1st to September 30th. The time 

 of flower-stem formation was reckoned from the day on which at least 

 one flower-spike of a plant in a series had emerged at least half-way 

 from its surrounding leaf-sheath. 



His results may be briefly summarised as follows. Exposure of the 

 seeds to low temperatures during germination or during the early seed- 

 Hng stage ensures that flowering shall occur during the first year (Plate I, 

 Fig. I; and cf. Appel and Gassner(i)). He carried the analysis further 

 and obtained the following quantitative results. Firstly, the lower the 

 temperature (over a range of 0°-25° C.) the shorter the. interval between 

 germination and culm-formation as is shown in Fig. 2, which we have 

 constructed from Gassner's data. Secondly, the earher in the develop- 

 ment of the plant the exposure to the low temperature occurs, the more 

 marked the result (see Tables V and VI; and cf. Gassner(9)). 



Table V. 



Effect of a loiv temperature at different stages in the development 

 of '' Petkuser" winter rye. 



Bate on which the 

 seedlings were 

 Date of sowing Treatment following the sowing planted out" Result 



'^A. Kept at Followed by a tempera-'' 

 24° C. for ture of l°-2° C. for 

 .30 hours 4 weeks 



/ Formed flowering- 

 stems irregularly 

 i from the begin- 

 ) ning of August 



March 18th /_ ^^^^ at Followed by a tempera- h ^P"! ^^^^^^ i Formed flowering- 

 l°-2°C.for ture of 24° C. for 30 stems regularly 



4 weeks hours | | from June 25th 



onwards 



* On April 16th the cotyledons of the plants belonging to series A were about 20 mm. 

 in length whereas those belonging to series B were about 30 mm. in length. 



