100 PLANT LIFE ON THE FARM. 



genus also occur, as between such structurally very closely 

 related plants as Poa trivial! 8, and P. pratensis, and 

 between the three species of Avena. On the contrary, 

 Bromus mollls and Poa trivialis are so far similar that 

 nitrate of soda is very favourable to them both. Poa 

 pratensis and Agrostis vulgari* concur in their liking for 

 ammonia with mineral salts, while they manifest opposite 

 tendencies with regard to nitrate of soda ; Poa pratensis 

 not being favoured by it, while the Agrostis is so con- 

 spicuously. 



These are only a few of the remarkable contrasts and 

 similarities that an inspection of the Rothamsted records 

 brings out. Perhaps the most striking point in this con- 

 nection is the opposite tendency manifested by different 

 grasses in reference to the action of ammonia salts, and of 

 nitrate of soda respectively, with or without mineral 

 manures in addition in each case. Doubtless, these char- 

 acteristics are to be correlated with differences of organ- 

 isation and structure, but with the exception that the 

 shallower rooted plants are often favoured by ammonia 

 salts, and the deeper rooting ones by the more deeply 

 percolating nitrate, little or nothing has been done in 

 definitely associating the different physiological endow- 

 ments above referred to, with corresponding differences of 

 internal structure. 



The Xieguminosae form a group of plants characterised, 

 BO far as this country is concerned, by the presence of 

 * papilionaceous " flowers like those of the common pea, 

 |y their leaves being compound, i.e., consisting of separ- 

 able segments, and by the production of a seed-pod, which 

 when ripe, splits into two valves or flaps ; this is technically 



