THE ORCHID REVIEW. 67 
matter to know the nature and habits of an enemy, otherwise, in groping 
about in the dark, all one’s energy may be uselessly thrown away. Much 
difference of opinion has been expressed as to the nature of this disease, 
and those who contended for its fungoid origin had at least some plausible 
reasons for their opinion, but it is now clear that the real cause is a sudden 
chill when drops of moisture are on the leaves, and that the fungi after- 
wards found on the spots are only there because the decaying tissue affords 
a suitable nidus for their development. In this respect they differ from the 
Vanilla disease, which is a true parasite. 
It is interesting in this connection to note that the late Mr. B. S. 
Williams always contended that the disease arose from wrong treatment, 
and was not infectious. Many years ago he wrote in his Orchid Grower's 
Manual—* The spot is the dread of Orchid growers. . . . Some assert 
that it is infectious, but this we do not believe. Indeed, we should have no 
hesitation in placing a plant infected with spot amongst a quantity of 
healthy ones.” He also pointed out that it was seldom troublesome under 
proper treatment. And it is further interesting to find that it was Dr. 
Lindley who first suggested the cause of the mischief. When at Hoddesdon 
two Phaleenopses became affected with spot in the winter, and a leaf was 
sent to Dr. Lindley, who replied “ ‘that the plants had been kept too moist 
during the cold dark days of winter’—a reply which we have never since lost 
sight of. He was quite right, for it was a sharp winter, and these two 
plants had been kept wet by placing the bottom of the block in which they 
grew in a pan of water to keep off the cockroaches.” Mr. Williams specially 
deprecated too much heat and moisture, as “ under such exciting manage- 
ment they [the plants] are apt to become spotted and get permanently into 
a bad state of health—in short, the least chill, after growing in so high a 
temperature, is liable to induce disease.” It is quite clear from these sone 
what Mr. Williams thought was the cause of spot, and Mr. aes 
experiments not only confirm this opinion, but also show the precise way 
in which it is brought about, which is important, and goes far to indicate a 
temedy, or, at all events, how to prevent it. 
The serious outbreak of Cattleya Fly noted at page 44, tiga aS 
allude to, if only to point a moral from the preceding paragraphs. ‘ a 
who have it should try to find out all they can about it, for ate a We 
Sense in the concluding lines of the article just a" a z yin, 
€xperience with the pest, but the remedies suggested on @ eng 
Stamping th€ pest out is obviously the proper SS ifone oad dae affected 
Set about it. A friend suggests the advisability of burning 
