254 '^^^ frisk Naftiralist, November, 



ferred to, where no oat crop was raised. So in this case also 

 there appears no doubt whatever but the weed seeds lay in the 

 soil since the field was last cultivated. 



Some observations bearing on the effect of severe frost on 

 seeds buried in the ground are worth recording. In the winter 

 of 1 90 1 -2 a number of weed and other seeds were put into a 

 shallow box containing about seven inches of soil. The soil 

 was saturated with water and put into an open place, where it 

 was left from 23rd November, 1901, to 7th August, 1902. 

 During the winter severe frosts occurred on fifteen nights al- 

 together. The following seeds germinated: — Horse Chestnut, 

 Radish, Wallflower, DiajitJuis barbaUts^ Curled Dock, Knot- 

 grass, Fumitory, Common Nettle, Orach e, White Campion, 

 Chickweed, Gefanmni disscchim, Goutweed, Angelica sylvestris^ 

 T?ifoli2Wi vmuis, Goosegrass, Purple Dead-nettle, Teasel, 

 Ve7 07iica arvc7isis, Greater Plantain, Groundsel, Annual 

 Meadow Grass, his Pseudaconis. On the 23rd December, 1901, 

 after four nights' continuous hard frost, so that there was ice 

 sufficiently strong for skating on, I examined the bare soil of 

 the garden (at Antrim) in an exposed place, and found that 

 the frost had penetrated to a depth of 4J inches. In a grass 

 field in an exposed part, where the herbage had been cropped 

 close, the frost had penetrated to a depth of 2| inches. In 

 neither case was there any snow on the surface of the ground. 



As seeds when buried in the ground are doubtless saturated 

 with water, it would seem fair to assume that most of those 

 in the top three inches of soil are frozen without being 

 injured. And yet the case is not by any means proved. It 

 is well known that salt water requires a lower temperature 

 to freeze it than fresh water, owing to the amount of salts 

 contained in solution. The protoplasm in the cells of the 

 seed contains a large number of organic and inorganic sub- 

 stances, and whether the temperatures reached in this country 

 are low enough to freeze it remains an open question. 



It remains somewhat of a puzzle why the seeds buried in 

 the soil lie so long dormant without attempting to germinate. 

 Three conditions are necessary for the germination of seeds — 

 (i) water, (2) a certain degree of temperature, (3) a supply of 

 air, or, speaking more strictl}', of oxj'gen. There is no 

 doubt but the first condition is fulfilled. The second condi- 

 tion is also complied with — at least in summer So that it 



