HYGIENIC CONDITIONS OF GLASSHOUSES 17 
suffered badly from ‘‘ damping off ”’ caused by a fungus, 
Phytophthora cryptogea. During the winter 1919-20 a 
heavy rain caused the drainage water from the high land 
to flood the depression below. The heap of soil by 
the watercourse was half submerged for about eight days, 
and remained in a sodden condition during the rest of 
the winter. The nursery in the depression had previously 
been free from ‘‘ damping off,’ but in 1920 an epidemic 
broke out which caused the death of thousands of young 
plants and threatened to prevent the cultivation of 
tomatoes for that season at least. Careful tests showed 
that the heap of propagating soil was badly infected, 
and indicated that infection had been introduced in the 
drainage brought down during the winter flood. 
In the second case, a tomato nursery lost 70,000 
plants from the same disease, and the infection was 
traced to the surface drainage water brought from 
another nursery, where tomatoes, asters, and wallflowers 
were badly attacked. It is thus evident that disease 
organisms in contaminated drainage are of immense 
importance, especially in areas where nurseries are con- 
gested together, and if a site is chosen in which there is 
danger from this source, the nursery should be protected 
by laying drains round it, so as to divert the natural 
drainage. 
Glasshouse Construction 
By reason of the marked improvements which have 
resulted from the evolution of modern glasshouses from 
the older types, and the consequent alteration in glass- 
house management, the grower is now in a better position 
to control the environment of his crops and to elimi- 
nate many troubles which formerly were of common 
occurrence. 
Of all the many factors which are intimately connected 
with the construction and management of glasshouses 
there is probably none which has not a direct bearing 
2 
