386 Decay in gromng Larch and Spruce. 



cause. As nothing satisfactory has been discovered on the 

 subject, I venture my opinion, which is, that this decay proceeds 

 from the too rapid growth of the trees when young, and from 

 their very slow growth when aged. In confirmation of my 

 opinion, I have sent you specimens from decayed, and also from 

 healthy trees, taken from the trunks and from the roots. 



When larch and spruce firs are young, they grow often 

 rapidly, and the wood formed at that period is very porous both 

 in the trunk and roots. As the trees advance in age, the supply 

 for their growth is less, from the soil being greatly exhausted, 

 and often from the trees not having been thinned out in proper 

 time. The outer case of wood then formed is less porous, and 

 becomes in time too compact to admit air to the early formed 

 wood within. This latter being of a coarse grain, the dry rot 

 begins to infect it, in the same manner as it attacks wood which 

 has been painted in a green state, the paint excluding the air 

 from the inside wood. The specimen No. 1., taken from the 

 root end of a decayed larch, is an example. 



The decay in the trees goes on more or less rapidly, according 

 to the grain of the wood. It ascends the trunk and makes its 

 way along the roots ; at least those first formed which have 

 become the conducting tubes to the trunk from the smaller roots 

 and fibres. As the disease advances, the sap collected in the 

 fibres passes with difficulty through the decayed conductors to 

 the trunk, and the trees become sickly, although the small roots 

 and fibres where the sap accumulates be healthy. This will be 

 evident in the root specimen No. I., cut off I ft. from the bole 

 of the tree. As farther proof that decay proceeds from too 

 quick a growth, the trees that have grown beside decayed ones, 

 but happened to grow slowly, have been found sound ; and it 

 may often be observed, in trees partly decayed, that it is the quick 

 growths in the trunk that are rotten. Specimen No. 2. shows 

 the former, and No. 3. the latter. 



Decay may, in some cases, have proceeded from other causes j 

 when trees make unusually large growths, as in specimen No. 4., 

 such wood cannot last long. In this specimen, however, the 

 outside wood is of fine grain. 



The supposition, that the soil is the cause of rot, is in a great 

 measure correct, if climate be taken in conjunction with soil. It 

 is a common observation, that a tree has got down to a soil 

 which it does not like. If the soil were in fault, the wood grown 

 then would be bad, whereas in reality it is the best. The ej-ror 

 lies in the supposition that the decay proceeds in age from soil 

 and climate ; but its foundation is actually laid in the youth of 

 the tree. In proof of this, it is a known fact that trees grown in 

 cold and barren situations are always sound. Their growths are 

 small, and the wood in consequence is durable. The best larch, 



