THE CONTROL OF PLANT DISEASES DUE TO FUNGI. 17 
sporium Potni Brooks),* Coniothyrium Fuckelii, Phoma Mali &c. ; 
in other cases the trouble has been regarded as of a physiological 
character (Scott — Jonathan apples), whilst Norton claims to have 
imitated some types of spotting by the action of certain gases- 
This fruit-spot is certainly on the increase in Britain. Every- 
one will agree that it is as important for us as for the United 
States to keep fruit clean both in the orchard and the store, whether 
offered for sale or grown for exhibition. But first we must be able 
to diagnose the symptoms and distinguish them from bitter-pit 
characters and to distinguish fungal from non-fungal spotting. If 
the spotting is of a fungal character, it is important to discover what 
fungi are implicated, their degree of parasitism and their hosts, for 
it does not at all follow that the fungi found here will be the same as 
those isolated in the United States or elsewhere, f (Fig. 1.) The 
success of practical schemes we may devise for combating this 
trouble will depend on our knowledge of these things. 
Again, there is a blemish so vexing to orchidists that appears in 
the form of spots, blotches, or mottlings in the leaves of some favourite 
or valuable Orchid. (Fig. 2.) This trouble has caused much contro- 
versy ; some argue, and on occasion quite rightly, that cultural condi- 
tions alone are to blame, whilst others maintain that fungi or bacteria 
are the cause. For a time the fungus Gloeosporium was thought to be 
the culprit, and species were described as causing spot on Oncidium 
(G. Oncidii Oud. —Amsterdam) , Odontoglossum (G. Bidgoodii Cooked- 
England), Cattleya (Gloeosporium sp.- — Paris), and other Orchids (G. 
cinctum B. and C. \ G. pallidum Karst. j G. orchidearum, Karst, on 
Mexican Orchids), whilst a species as yet unnamed was found at Wisley 
in 1 91 5. But the evidence in most cases is merely that of association. 
We do not know at all to what extent these fungi are able to cause 
disease in Orchids. To obtain this information one must cultivate the 
fungi and understand their behaviour. More recently several instances 
of spotting due to bacteria have been recorded. Pavarini has 
described no less than four new species — Bacterium Cattleyae, Bacillus 
Polacii, Bacterium Krameriani, and Bacillus Farnetianus, which he 
has isolated from and reproduced spotting by inoculation in Cattleya 
Harrisoniae, Odontoglossum citrosum, Oncidium Kramerianum, and 
Oncidium ornithorhynchum respectively J in Japan, Hori has obtained 
a bacillus causing brown rot in Cypripedium — Bacillus Cypripedii. 
* Brooks first described his fungus as Cylindrosporium Pomi in Bull. Torr. 
Club 35, 423-456 (1908) but later, on incomplete evidence, transferred it to 
Passerini's Phoma — Phoma Pomi, for which see Charles Brooks and Caroline 
A. Black in Phyt. ii. (1912) , pp. 63-72. The supposed Cylindrosporium fructifica- 
tion is therein regarded as a Cylindrosporium stage in the life-cycle of the Phoma, 
but this organ is very unlike the characteristic acervulus of a Cylindrosporium 
which in the case of C. Padi has been clearly described by B. B. Higgins in 
Amer. Jour. Bot., vol. i. No. 4, pp. 145-173 (April 1914). 
f I have succeeded in isolating several fungi in pure culture at the Patho- 
logical Laboratories of the Imperial College of Science, including species of 
Stemphylium Alternaria arid Pleospora from spotted areas in certain varieties 
of British apples ; see " Rept. Sci. Com. Roy. Hort. Soc." Journal R.H.S* 
xli. p. cv. 
VOL. xlii. C 
