SCIENTIFIC COMMITTEE, NOVEMBEE 21. 
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leaves also are narrower Mr. Wilks observed that he has had it for 
eighteen years, and that it is remarkable for its very vigorous growth, 
being also very nearly hardy. Mr. Im Tlinrn remarked that it is very 
abundant in British Guiana, and is so close to H. equestre that it would 
seem to be a form of that species. 
Liliujii giganteum, Cai^sulc. — Mr. Wilks brought a ripe capsule of 
this species, and alluded to the readiness with which it ripens abundance 
of seed in various localities in this country, and the ease with which it 
can be raised from seed, giving opportunities for producing varieties. 
Canker on Apple Trees. — Dr. William G. Smith sent the following 
report on specimens received in October, and forwarded to him for 
examination : — 
A specimen of this canker was received recently with a request for 
some information on the cause of this common trouble. The case sent 
I consider a typical form of canker caused by the ascomycete fungus, 
Nectria ditissuna. The action of this fungus in causing canker was first 
described by Robert Hartig [Untersuchimgen auf d. forst-hotan. Institut. 
(Munich) I. p. 209, 1880). Good descriptions are given in the English 
translations of Hartig's and Tubeuf's text-books, in G. Massee's recent 
text-book, in H. Marshall Ward's Timber Diseases, and by C. B. 
Plowright in the Gardeners' Chronicle, April 19, 1884. It is unnecessary 
to repeat here the details given in these works. The reasons for consider- 
ing Nectria as the chief agent in the present case are : — (1) Near the 
centre of each of the three canker areas sent is the dead stump of a side 
twig, which, by being pruned or broken would afiord an entrance to 
Nectria — a w^ound fungus. From this point the canker has spread, up, 
down, and round the still living main branch. (2) The presence of two 
forms of spores of Nectria. In one branch the external canker has 
passed over into a form of wood-rot, w^hich is passing along the inside of 
the branch. 
" This is one form of Apple-tree canker, but is not the only form. 
The condition which disposes a tree to canker is a wound deep enough to 
penetrate the softer tissues of the bark. This may be caused by the 
pruning of twigs, or by their being broken or gnawed ; it might also be 
due to a deep crack in the bark, such as one sometimes sees on trees as 
the result of excessive growth or internal pressure ; or it might be a crack 
in the bark caused by sun or frost, or the killing-back of immature twigs 
in winter. (The latter case Hartig distinguishes as frost-canker, capable 
of extending each successive winter without the agency of fungi.) Given, 
then, an open wound, the soft tissues exposed offer a suitable substratum 
for the growth of fungi, bacteria, or animal organisms. The tissues of 
the Apple-tree seem well suited for the growth of Nectria ; and, v;hen 
one considers the common occurrence of the fungus as a saprophyte, on 
dead wood, or as a parasite on many kinds of trees, it is not surprising 
that it is the fungus which generally establishes itself. Hartig and others 
have proved that, having obtained a footing on a wound, Nectria is able 
to attack the living tissues, and gradually to bring about a canker. In 
the same way any other organism with a partiality for the tissues of the 
Apple-tree may, individually or in company, be an agent in converting a 
wound into a canker ; for instance, at least three species of Polyporus 
