r9^4- Adams — Vitality of Seeds. 255 



would seem that it must be want of air that keeps the seeds 

 from germinating. On the other hand, the roots of the 

 herbage descend to as great a depth as that at which the 

 seeds are buried, and yet they require oxj^gen for their proper 

 respiration. But as very little is known on the respiration 

 of roots, it would be useless to base a comparison on that. 

 Another possible reason why the seeds lie dormant is that, 

 owing to the pressure of the superincumbent earth, the 

 embryo is unable to force its way through the seed coat. 

 When the ground is broken up some of the seeds are brought 

 up nearer the surface, where the pressure is less and there is 

 a better supply of air, and, if they have not been buried too 

 long, they germinate. 



In the case of some seeds, at least, it seems that a supply 

 of moisture tends to prolong their vitality. I have repeatedly 

 saved the seed of Yellow Rattle, kept it dr>^ the following 

 winter, and tried to germinate it in spring, but without result, 

 as it had lost its vitality. On the other hand, the seeds which 

 have fallen into the ground produce a plentiful supply of 

 plants in the following spring. 



Possibly there may be some readers of the Irish Natiualist 

 acquainted with old pastures of which the age is known for 

 certain. If so, it would be interesting to have a few sods 

 removed here and there in order to see what kind of annuals 

 will turn up. 



Royal College of Science, Dublin. 



ICHNKUMONID^ AND BRx\CONID^ FROM THE 



NORTH OF IREIvAND. 



BY REV. W. F. JOHNSON, M.A. 



I HAVE picked up from time to time a few of the parasitic 

 Hymenoptera. The publication of Mr. Morley's work on the 

 British Ichneumons caused me to look up my notes, and 

 some unnamed specimens that I had in one of my store- 

 boxes. I find I have a list, which, though small, may be of 

 some interest to readers of the Irish Naturalist. I am indebted 

 to Mr. J. B. Bridgman and Mr. Claude Morley for kind 

 assistance in determining the species. 



A 2 



