24 
vention. That is to prevent the outbreak of disease in the first 
instance, or, if it has once appeared, to prevent its further spread. 
Though the rules and precautions to be adopted are simple 
enough, still they are extremely difficult to put into practice. 
It is only within recent years that cultivators in general are 
beginning to realise how infectious many plant diseases are, but 
even yet in the majority of cases it is only after a disease has 
become epidemic and has occasioned considerable and _ irre- 
parable damage that the advice of the plant pathologist is sought. 
There are cases enough on record where valuable crops can 
no longer be cultivated owing to the ravages of disease which 
might have been prevented from occurring at all, or at least 
checked or considerably modified in its early stages. Such has 
been our unfortunate experience with the European larch. As 
the result of planting in unfavourable soils and situations, its 
predisposition to canker caused by Peziza Willkommit has been 
so much increased as to very seriously interfere with its pro- 
fitable cultivation. It is therefore not surprising that attempts 
have been made to find a substitute in the shape of some other 
species of larch which would resist the ravages of the canker 
fungus. 
Within comparatively recent years two species have been 
introduced in the hope that they would be less liable to attack, 
if not immune from the disease. These two species are Japanese 
larch (Larix leptolepis) and the western larch (Larix occidentalis). 
e western or occidental larch was discovered in the year 
1826 by Douglas, but over fifty years elapsed before it was 
introduced into this country. For some reason or other, possibly 
the difficulty in securing seed, and consequently through the 
scarcity of plants, this tree has not become very widely known 
in Britain. Mr. H. J. Elwes, after several attempts to secure a 
supply of seed, was finally successful in securing a small quantity 
in the year 1903. This he distributed to arboriculturists in many 
parts of the country in the hope that this species would be “‘ less 
liable to the attack of P. Willkommit than the common 
larch.”” Speaking of the germination of the seed which he dis- 
tributed, Mr. Elwes says: “ The seedlings raised in 1904, from 
the seed which I distributed, have grown in several places, best 
perhaps at Murthly, under the care of Mr. Lawrie, where in 
September 1906 I saw some hundreds thriving very well, though 
not so large as the common larch of the same age.” 
In the winter 1908-09 two specimens were sent from Murthly 
to the Royal Botanic Garden, one of which had, unfortunately, 
developed unmistakable symptoms of attack by P. Will- 
kommit. This plant is shown in Plate V, Figs. 1 and 2. 
The cankered portion, as will be seen in Fig. 1, is situated at 
