ON THE DISEASE OF THE LARCH. 141 



and heart, known as heart-rot; (2.) Blister or cancer; and (3.) 

 Insect or blight. The first of these diseases is the most disastrous, 

 being found under a great variety of circumstances, and apparently 

 not peculiar to any soil or situation. The cause I have found, 

 without exception, to be mutilated roots. When larch is planted 

 on soil no matter how good, if the subsoil is unfavourable, heart- 

 rot sets in when the tree is from fifteen to thirty years of age, the 

 time of its attack being regulated by the depth of the hard subsoil 

 from the surface, or the time the roots take to penetrate to it. 

 After the roots are in, or in contact with a hard stony subsoil of 

 whatever formation, the surface soil being invariably softer, sub- 

 jects the roots to a large amount of friction when the tree is agi- 

 tated by storms. The roots, by the surface soil yielding and the 

 subsoil remaining stiff and stubborn, lose many of their spongioles 

 and the underside of their bark, and, being thus mutilated, imme- 

 diately cease to be of any use to the tree, either by way of supply- 

 ing nourishment or throwing off excrementitious matter. After 

 a while these mutilated roots absorb moisture from the soil, and 

 in course of time begin to rot, the tissue being attacked by micro- 

 scopic and other fungi The disease presses slowly upwards, and 

 eventually the tree dies or is blown over. This is not the case 

 when the tree is grown on fissured rock, because the base is set on 

 a solid*foundation, the roots being held firm in the rock, the bole 

 only is subjected to the pressure of storms. If the mutilation of 

 the roots takes place during the latter part of the year, while the 

 sap is descending, the wound may get sealed up with resinous 

 matter. Unfortunately for the larch, its roots generally get 

 damaged in the early summer, being at that time in full leaf, and 

 presenting a greater resisting surface than in winter, when the 

 foliage is off. 



Scotch and spruce firs are also subject to the same diseases, and 

 from the same cause. 



In the case of the Scotch fir, however, though its roots be muti- 

 lated, yet from the nature of the tree, and it generally receiving 

 the damage during the winter season, the resin, by sealing up the 

 roots and thus excluding all unnatural moisture and other dele- 

 terious matter-, prevents the heart-rot. 



Some years ago I was called upon to examine, value, and dis- 

 pose of a mixed plantation of nearly 300 acres in extent. A por- 

 tion of this was planted on arable and part on heathy soil. The 

 situation of the whole wood was at an average of 800 feet above 



VOL. VIII., PART II. K 



