This section is from the book "The Gardener's Monthly And Horticulturist V26", by Thomas Meehan. See also: Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long.
In an elaborate discussion on disease in the peach Professor Penhallow says: "Fungi do not penetrate normal cellular structure, but remain confined to the dead tissues, or those of low vitality." Further on, discussing of the curl, he remarks, "As the fungus causing the disorder (Exoascus deformans) matures, the leaves become more and more curled and finally fall off during the month of June".
If fungi cannot penetrate the normal cellular tissues of leaves, it is not clear how they can cause the disorder known as curl or any other disorder. But in view of the researches of Berkely and others, it seems rather late in the day for the assertion that fungi cannot attack healthy vegetation, and thus produce disease, and which the Professor's own expression about the "curl" seems rather to confirm.