THE DISEASES OF TIMBER TREES. 61 



transplanting in the year of the disease, and are frequently rendered 

 unfit for transplanting at all. 



The explanation at first given of this morbid appearance was 

 that it was due to dessication or drying up of the haves (accord- 

 ing to Ebermayer), occasioned in winter and early spring, when, 

 owing to bright warm sunshine, the foliage was stimulated to 

 strong active transpiration, whilst the frozen ground could not as 

 yet yield the necessary supplies of soil-moisture ; thus much the 

 same process of exhausting the water in the stem, and drying up 

 the tree, went on, as can take place in the case of continuous heat 

 and drought in summer. The leaves become regularly and equally 

 brown all over, and show no traces of fungoid growth. From many 

 observations it appears probable that in not a few cases the cause 

 I of this leaf-shedding is to be looked for in this process of drying 

 j up or dessication ; hence the practice, often recommended and 

 | applied, of covering over seed-beds during winter and spring with 

 branches or frame-work, and the formation of temporary nurseries 

 under the lee and side protection of older crops, must be admitted 

 to be a good practical means of obviating this effect of insolation. 

 These protective measures will, however, be of no avail, and may 

 indeed be directly and actively injurious, when the disease of the 

 foliage is caused by Pine scab or scurf (Hysterium pinastri), as can 

 also be the case, according to many experiments and observations 

 (made by Prantl, Hartig, Tursky). Here the leaves first show in 

 autumn a lightly mottled appearance, occasioned by the mycelium 

 of the fungus developing in the interior of the foliage. In the 

 following spring the needles rapidly assume an entirely brown 

 colour, die off, and show the spermogonia of the fungus as black 

 pustules, into which the dark spots have now developed. But as 

 the spores are scattered and carried across to young foliage by 

 ! the wind in May and June, producing first of all disease in the 

 I autumn, and death in the following spring, the state of the 

 I weather at the time of the ripening of the spores is certainly of 

 ; great influence as regards the spread of the disease. And in the 

 i face of this circumstance, any covering of the seed-beds with Pine 

 j twigs, on whose dead foliage the fungus is apt to be found in 

 j considerable quantities, would be just as risky as the formation of 

 seed-beds inside old Pine woods, or the continuous use of tem- 

 porary nurseries where seedlings have already been killed off by 

 i this leaf-shedding disease. 



