1922.] Depth of Sowing Grass and Clover Seeds. 



59- 



A rough suitaee very materially assists the seedling'^ to become 

 attaclied to the soil. Two series of tests were put up : in one 

 case the seeds were sown on the surface on soil previously pressed 

 and in the other on a non-pressed surface ; in the former case 85 

 per cent, and in the latter 63 per cent, of the seedlings bccanu? 

 fixed to the soil. It would thus appear obvious that the soil 

 should not be rolled prior to sowing when it is not intended to 

 cover the seeds. 



Germination is slower from surface than from covered seeds; 

 and especiallv so if the soil is inclined to be fairly dry. The 

 following figures giving the percentage of germination fourteen 

 days after sowinr>" show the extent of the difference : — 



Surface. At ifh in. 



Pot Cultures 52 88 



Box 36 90 



Effect of Light on Germination. — That hght has not the same 

 detrim.ental (or even any retarding) effect on the germination 

 of red clover seeds as it has on the germination of certain grass 

 seeds* was shown by the foUov/ing experiment. Tn order to 

 equalise evaporation a number of surface sown pots were covered 

 with large petrie dishes, half of which had been made imperme- 

 able to light by covering them with thick, brown paper. Both 

 series were allowed to germinate under normal room conditions. 

 The average results after 10 days' oermination v^ere : — 



Germination. 



Exposed to light 95 per cent. 



Kept in the dark ... ... ... ... ... I'O per cent. 



The Behaviour of Red Clover Seeds when Covered at different 

 Depths. — The seeds were sown at 12 depths varying from J in. 

 to C) in. round the sides of large glass tubes in order to keep the 

 seeds and seedlings under observation. The tubes were covered 

 with brown paper and kept in a dai-k room at ordinary tempera- 

 ture (maximum about 12° C.). 



It was found that the seeds germinated equally well and at 

 about the same rate at all depths down to 1 in. — the percentage 

 germination at these depths only varied from 75 per cent, to 

 85 per cent., but at 5 in. only 10 per cent, of the seeds germi- 

 nated, while at G in. not a single seed germinated although 

 water was imbibed by the seeds. The failure of the seeds to 

 germinate at depths of 5 and G in. was no doubt due to lack of 



* Contributions reji^ardin.a: the jrermination of unhullod and naked Tiniothv 

 seeds. Bv M. Heinrich T.andw. Versurlist. 9.'^ : Botanical .\bstracts, Vol. VI I, 

 Xo. a, 1921. 



