PLANT DISEASES AND FUNGI.
21
to the attacks of insects, of various kinds, which it is the province of
the entomologist to investigate. Undoubtedly, the attention of
farmers, and others interested in agriculture, was directed to insect
pests for years before the slightest effort was made to check the
ravages of fungoid parasites, and even before fungi were reckoned
as a factor at all in the production of disease in crops.
In addition to these two causes, the most common and most
injurious, there are other subsidiary elements which tend to disease,
such as bad cultivation, insufficient drainage, overcrowding, uncon-
genial soil, impure air, external injuries, and, as we believe, hereditary
transmission. Of all these, our remarks are intended to apply to
diseases having a fungoid origin.
It has been objected by some writers that fungus diseases are in
no sense hereditary, but are communicated externally to each
generation of young plants, and therefore when infection is provided
against, all that is necessary has been done. This we hold to be a
dangerous deception in the face of the following facts: "A well-
known nurseryman, in a large way of business, had imported seeds of
Dianthus direct from Japan. These seeds were carefully grown
under glass, and, immediately they were up in the seed pans, they
were all attacked and destroyed by Puccinia lychnidearum. On
making a microscopical examination of a series of the seeds,
mycelium was detected inside the integument which surrounded the
embryo, or infant plant, and within the coat of the seed."3 It may
be explained that the mycelium is the first stage in the development
of fungus disease, and consists, for the most part, of the slender
delicate filaments which result from the germination of fungus spores,
or from the rejuvenation of portions of a hybernating or perennial
mycelium.
Many years ago we were consulted on the condition of certain
celery plants in a garden at Hampstead. Two or three rows of
plants were in a perfectly clean and healthy condition; but one or
two rows of plants growing beside them were covered with pustules
of the celery brand, Puccinia apii, and thoroughly useless. Upon
inquiry we found that the healthy plants had been raised from an
old stock of "saved" seed ; whereas the diseased plants had been
raised from other seed which the gardener had begged from a friend,
because his own seed was insufficient for planting all the ground he
wished to cover. AU the diseased plants were at once rooted up
3 "Gardener's Chronicle," 26th January, 1884.