212 TKAXSACTIONS OF ROVAL SCOTTISH ARBORICULTURAL SOCIETY. 



Haak has done good work in at last placing the biology 

 of the Lophodennhi/n fungus on a sound basis, and as a 

 practical result of his researches lays down the following : — 



r. As regards the selection of seed : this selection should be 

 based entirely on silvicultural requirements, a high percentage 

 of germination being essential. 



2. Infection caused by the spores ejected from tlie apothecia 

 takes place in a dangerous degree only from about the middle 

 of July till the end of September. 



3. The spores are formed on the leaves of old pine trees as 

 well as on those of young growth The strongest development 

 of spores takes place on cultivated areas, the least in mixed 

 forests with a rapid decomposition of the litter. The danger of 

 infection is therefore largest in the former case and negligible in 

 the latter. 



4. The infection is eitlier effected at a distance over large areas 

 by spores floating for some time here and there with air currents, 

 or it is a local one in the immediate vicinity of the leaves bearing 

 apothecia, being, so to say, reciprocal. 



5. Nurseries must be established as far as possible from scab- 

 attacked cultivations and thickets, in localities not liable to 

 infection. For forests in which these conditions cannot be 

 found plants must be obtained from outside. Where such 

 localities are rare, permanent nurseries must be formed, in which, 

 by means of suitable manuring, healthy plants can be raised 

 year by year, and which can be kept scab-free. 



6. In order to avoid or diminish the danger of local infection — 



{a) Sowing and planting in nurseries should not take 

 place in the same place or near each other ; 



{b) Only the best and soundest seedlings should be planted; 



{c) The seedlings not considered fit for transplanting 

 should be effectively destroyed; 



(d) Thick sowing in the open should be avoided ; planting 

 is preferable. 



7. All means must be adopted to bring the cultures as rapidly 

 as possible through the susceptible age. A thorough working 

 up of the soil, selection of the best .seed, and the use of the 

 strongest plants, grown on good soil only, are essential, as well 

 as a subse(juent careful treatment of the young cultivations 

 by hoeing, grass cutting and syringing. Every case of filling 

 up blanks in the cultures prolongs the period of danger. 



