68 



draw your attention to the fact of Hiltner's (45) pointing out in 1906, that 

 lowering the temperature in alternating naight be preferable to raising it. 

 Heinrich (56) also recommends temperatiu'es between 5" C. and 20° C. for 

 Aathoxanthum odoratum. Honcamp (57) exceeds them, suggesting, for 

 that special grass, a constant temperature of 5° C. Harrington likewise 

 applies lower temperatures than are generally used, but not, however, 

 lower than 15° C. 



Without unnecessarily wearying you with long lists of the results of 

 comparative germination tests carried out at Wageningen, I may mention 

 this method as a very suitable one, especially for the following seeds : — 

 ^Alopecurus pratensis, Apium graveolen s, Arrhenatherum elatior (husked,) 

 Avena fiavescens, Cichorium Endlvia, Dactylis glomerata, Lepidium 

 sativum. Nasturtium officinale, Poa species (Poa- compressa excepted), 

 Solanum Lyeopersicum, &o. Very suitable, too, though not yelding 

 specially higher results, is this method for Agrostis stolonifera, Cichorium 

 Intybus, Petroselinum sativum, Daucus Carota and Festuca pratensis. 

 It may be observed besides, that (with the " Copenhagen alternating " 

 method) the germinating seeds are always exposed to the diffuse light of 

 a northern room. Comparative tests, exposed to direct sunlight, did not 

 offer ajiy better results, even for the Poas (with the exception of Poa 

 compressa). 



To those of the audience who have not yet tried the alternation of 

 temperature between 11° C. and 25-28° C, I may strongly recommend the 

 comparative testing on the Jacobsen incubator. In many cases, better 

 results will be obtained than with other germination methods in use. 



I shall dwell a little longer on the second subsection, the seeds requiring 

 a constant low temperature as the best means for a most favoiirable 

 germination, because a temperature of 10° C. for normally ripened seeds, 

 so far as I am aware, is not yet recommended as a normal germinating 

 naethod. Here the seeds remain during the first five days at a temperature 

 of 10° C. in the incubators already mentioned (cooled by brine). After that 

 time they can be placed in a 20° C. incubator. One word as to why a tempera- 

 ture of 10° C. has been chosen. In this choice, on the one hand, it was 

 necessary to reckon with the evident inclination of some seeds for germina- 

 ting at a low temperature ; on the other hand, it had to be kept in mind 

 that the germinating temperature should not be chosen so low as to lose 

 all the advantage obtained from it, on account of too great a slowness in 

 the course of the germinating process. It was for these reasons, after 

 some preliminary experiments, that the temperature of 10° C. was chosen. 

 For various kinds of seed this method, compared with other methods, was 

 not always successful, as imdoubtedly it was not the best method for Allium 

 Cepa, Phaseolus pratensis and Pastinaca sativa, though all these are seeds 

 which germinate well at 20° and are badly influenced by higher tempera- 

 tures. Omithopus sativus and Lepidium sativum did not show any differ- 

 ence. With some kinds, however, the new germinating temperatiu-e 

 proved to yield a considerable and almost constant rising of the germination 

 percentage. Spinach may be taken as first and principal among them. 

 For the greater part of the comparative tests, the temperature of 10° C. 

 proved to be better for this seed than that of 20° C. used up till now. 



In view of the great importance that the. testing of spinach seed 

 possesses for xis (at Wageningen some hundreds of samples of spinach 

 seed are investigated yearly), the comparative experiment between 10 and 

 20° C, was continued with a great number of samples. 293, or 94 per cent, of 

 the 310 samples tested, showed better or equal results, 17, or 6 per cent., 

 were only slightly lower. In this last case the difference only amounted to 

 one or two per cent., some cases excepted, and so the result was not much 

 inferior to the one obtained by the 20° method. The differences in 

 favour of the 10° method were of much more importance as the following 

 list will show. 



