The seeds of many species of plants have a habit of germinating in unexpected places under various conditions, and the question of the vitality of seeds is one that has frequently engaged the attention of scientists. It has often been claimed that seeds obtained from old pyramids and sepulchres have germinated when placed in favourable circumstances, but Becquerel states that strict enquiry and experiment show that authentic seeds of such origin will not germinate, but that the seeds so obtained which do germinate have proved to be frauds inserted by the fellaheen for the sake of gain. Various writers (quoted by Becquerel) have claimed the power of germination for seeds buried for very long periods. Michelet claimed that seeds of Galium anglicum, buried 3000 years ago in the valley of Doubs, had retained their power of growth; von Heldreich, that Glaucium Serpieri from land covered by excavated scoriae 1500 years ago, was still viable; much doubt, however, has been thrown on the authenticity of such seeds.

Nitrogen, one of the most important plant nutrients, is present in the soil mainly as organic compounds which, with certain exceptions, are not, in those forms, assimilable by ordinary cultivated plants. The organic compounds undergo a series of chemical changes before they are ultimately changed into nitrates which are practically the most useful compounds of nitrogen which can be taken up by plants.

The experimental results submitted in the preceding pages may be summarised as follows:

Seven English soils have been examined in order to ascertain the validity of Greig Smith’s claim that partial sterilisation effects may be due to the destruction of bacterio-toxins in the soil. The results obtained with six of these soils show that:

1. The untreated extracts of these soils varied largely in their suitability for the growth of the test organism (B. prodigiosus). In some instances vigorous growth occurred; in others the numbers of introduced organisms fell to a minimum.

2. Treatment of the extracts by heat (which was supposed to result in the destruction of “toxins”) invariably led to still further bacterial decreases.

3. Extracts of soils treated with antiseptics (which are not supposed to destroy “toxins”) were on the whole more favourable for growth than those of untreated soils. Such extracts were found to have appreciably more organic nitrogen compounds than extracts of untreated soils.

The following Report on the contents of 311 pheasant crops presents the results of a very laborious investigation undertaken by Miss A. F. C.-H. Evershed during 1915 under my direction. Only those who have themselves attempted it will fully appreciate the amount of time and trouble involved in identifying the fragments of insects and plants met with in such a research.

The foregoing experiments give definite evidence, corroborative of the work of Koch, Remy and others, that the nitrogen content of sand or soil may be appreciably increased by the activity of Azotobacter when some suitable source of energy is supplied. For this purpose sugars such as dextrose and saccharose are suitable, but distinct gains have also been obtained by the use of plant residues. In laboratory experiments an increment of upwards of 6 mgrm. of nitrogen per gram of plant residues occurred, but in pot experiments gains of 9 mgrm. per gram of substance were obtained.