19 



(5) Plants are grown right through to fruiting and the produce 

 weighed. 



VIII. "O/i the Growth of Plants in Partially Sterilised 

 Soils:' E. J. Russell and F. R. Petherbridge. 

 Journal of Agricultural Science, 1913. 5, 248-287. 



Seven important directions have been found in which partially 

 sterilised soils differ from untreated soils as media for plant growth. 



(1) There is generally a retardation in germination but some- 

 times partial acceleration (i.e., affecting some of the seeds only). 



(2) There is generally an acceleration in growth up to the time 

 of the appearance of the third or fourth leaves, but sometimes 

 a marked retardation, especially in rich soils heated to 100°C. We 

 have failed to discover the conditions regulating the retardation, and 

 can never predict with certainty whether or not it will set in. On 

 the whole we have observed it more frequently during dull winter 

 days than in the brighter spring or summer days. 



(3) When this retardation occurs it is accompanied by a very 

 dark green leaf colour and either the formation of a purple pigment 

 or a tendency for the leaves to curl towards the under side. The 

 whole appearance is strongly suggestive of an attempt on the part 

 of the plant to reduce assimilation. 



(4) Later on the purple colour goes and the curling ceases; 

 rapid plant growth then takes place. The subsequent growth is 

 finally proportional to the amount of food present. 



(5) Plants grown in soils heated to 100° show a very remark- 

 able development of fibrous root unlike anything obtained on un- 

 treated soils. 



(6) Plants grown on soils heated to 100° have, in comparison 

 with those on untreated soils, larger leaves of deeper green colour, 

 stouter stems, usually shorter internodes ; they flower earlier and 

 more abundantly, and contain a higher percentage of nitrogen and 

 sometimes of phosphoric acid in their dry matter; the roots and 

 stems give up their nitrogen, phosphorus, and potassium more com- 

 pletely to the fruit. 



(7) Plants grown on soils heated to 55 or treated with volatile 

 antiseptics show fewer of these effects ; there is only rarely a re- 

 tardation in seedling growth but usually an acceleration, sometimes 

 a rapid one, succeeded by a period of steady growth which is finally 

 proportional to the amount of plant food present. No specially 

 marked development of fibrous root or shortening of the internodes 

 occurs, but there is an increase in the percentage of nitrogen and 

 sometimes of phosphoric acid in the dry matter as compared with 

 plants raised on untreated soils, and also a more complete trans- 

 location of these materials to the fruit. 



IX. The Effect of Bastard Trenching on the Soil and on 



Plant Growth. E. J. Russell and S. U. Pickering. 

 Journal of Agricultural Science, 1913. 5, 483 — 496. 

 Bastard Trenching as originally performed, consists of two 

 distinct operations ; loosening the lower spit of soil and digging into 

 it farmyard manure or other fertilising material. 



The experiments described in this paper were made on plots that 

 had been bastard trenched to a depth of three spits, but not manured. 

 The first and second spits were put back in their natural order, but 



