ROOT ROT OF CONIFEROUS SEEDLINGS. 49 



"4. In June and July, when the soil conditions were much 

 improved over those of early spring, many cases of recovery 

 from the disease were observed, as shown by the fact that 

 new roots had developed in the region of the root collar. At 

 this time seedlings which were recovering and forming new 

 roots could be detected very often by a glance at the tops. If 

 these were starting a belated growth, inspection of the root- 

 system in every case would reveal, usually, one or sometimes 

 more new roots, conspicuous by reason of their white colour, 

 their thickness, and origin high up, near the base of the stem. 

 Such recovery, which was of fairly common occurrence, is 

 more in line with a physiological trouble, than a disease caused 

 by a parasitic fungus. 



"5. The course of the disease was slow, requiring at least a 

 month for its completion. In many cases, even after three 

 months of growth, i.e. about August, the tops still appeared 

 healthy, although the year's growth had not developed, and 

 examination of the roots showed them to be apparently dead. 

 Here a considerably longer period would have been necessary 

 before the plants entirely succumbed. A very gradual death 

 of this sort would not be expected if the trouble were due to 

 the attack of a parasitic fungus. 



" 6. In soil of a similar character, in another part of the 

 nursery, which had been thoroughly limed, and contained a 

 generous amount of humus, such a disease had never been 

 known to occur. This soil was loose and porous, never retain- 

 ing water on its surface for any length of time. 



" The conclusion is, therefore, that the disease was due to lack 

 of oxygen trouble in a soil which was saturated with water, i.e. 

 that the roots were suffocated. 



" As already intimated, the remedy would consist in a thorough 

 liming of the soil. Probably this in itself would be sufficient, 

 but the addition of more humus would also improve the 

 physical character of the soil as well as benefit the plant 

 growth directly." 



VOL. XXXI. PART \. 



