I905- 



69 



NOTES, 



BOTANY. 



The Vitality of Seeds. 



I have been always greatly interested in the vitality of the seeds of 

 farm weeds. For 60 or 70 years we have kept a book here which shows 

 how each field has been annually cropped. 



Take the " Pond field." It was laid down in grass in 1886, and so 

 remained until 1903, when it was sown with turnips without any farm- 

 yard manure ; yet Fiimaria, Atriplex erecta, Chenopodiiim albtwi, Polygonum 

 aviculare, Papar-'er rhccas all appeared, not plentifully, as is usually the 

 case, but fairly frequently, also scattered plants of Sinapis arvensis. On 

 the other hand, Stellaria media and Capsella (very common weeds) were 

 rare or absent, and Eqiiisettim arvense, once common on part of the field, 

 had disappeared. The surface was ploughed and cross-ploughed and 

 grubbed and thoroughly mixed up for the green crop— therefore it is 

 hard to say whether the seeds were originally on the surface or not. 

 This field was top-dressed when in pasture once or twice in the 17 years. 



It occasionally happens, however, that we break old lea for a corn 

 crop. For example, "Wall's field" was laid down in grass in 1869, and 

 so remained until 1893. I well remember how surprised we were that 

 year to see Sinapis arvensis (" Prassaght") dotting the field of oats with 

 yellow patches here and there. My friend, Mr. S. A. Stewart, suggests 

 that winds, birds, etc., carry seeds to the surface of pasture fields. The 

 wind carries none of the seeds I have mentioned, and when the surface 

 is ploughed for oats with a " chilled plough " it is turned completely 

 upside down, and what was on the surface is buried 7 inches below it 

 after the ploughing, and seeds of farm weeds buried this depth do not in 

 my opinion germinate — I wish they did. 



In 1903 I took on lease for ever a field of about 16 acres adjoining my 

 farm. It had been treated so badly that I knew any crop sown on it 

 would be half smothered with "Prassaght" The field was yellow with 

 it the previous two or three years, so I decided to sow nothing for a year. 



When the days began to get warm and sunny the Prassaght soon 

 showed itself everywhere. I ploughed it all down and turned up a 

 fresh surface, when another crop showed itself; this was again ploughed 

 down and the process repeated six or seven times in the year, on each 

 occasion taking care as far as possible to expose fresh soil. I am sorry 

 to say that the potato crop sown after the fallow in this field in 1904 was 

 full of "Prassaght," notwithstanding the millions of seeds destroyed, 

 and no plants had ripened their seeds for eighteen months. The " Pras- 

 saght " occurred chiefly in the deep alleys of the V-shaped drills. 



Mr. Adams gives three conditions as necessary for the germination of 

 seeds— water, warmth, and oxygen ; there is a fourth, i.e., light, which 

 if not a necessity, is certainly a wonderful stimulant. 



