94 BACTERIA IN RELATION TO PLANT DISEASES. 
GENERAL CONSIDERATIONS. 
LOCATION OF THE LABORATORY. 
If possible, the laboratory should be in a clean building in the middle of a green 
lawn. If it must be in a crowded and dirty city it should be on an upper floor, as 
far removed as possible from the dust of the street and from the tramp of feet. It 
ought not to be located on streets filled with the dust of heavy traffic. Ifa ground- 
floor or basement room in a dirty locality is the only available place, then the air 
which enters the room should be filtered through absorbent cotton. A south front 
is desirable for the mounting of a heliostat and for other photographic purposes; 
a north light is desirable for microscopic use, if one is to work at the instrument 
continuously. By arranging one’s time according to the position of the sun, the 
light from east or west windows may be used to advantage five or six hours a day, 
which is quite long enough to fatigue ordinary eyes. The writer has managed to 
-get along very well without 
north light for the last ten 
years. If one decides to use 
with the microscope only ar- 
tificial light, such as that of 
the Welsbach burner, work- 
rooms for this purpose may 
be located anywhere. If pos- 
sible, several rooms should 
be secured and apportioned 
to the various kinds of work, 
é.g., general laboratory rooms, 
chambers for special workers, 
. sterilization-room, thermo- 
stat-room, cold-storage and 
stock-culture rooms, storage 
rooms. for chemicals, small’ 
glass-inclosed rooms for transfer of cultures, photographie rooms, dark rooms for. 
developing, etc.. The general photographic rooms should have overhead light as’ 
well as side light. k = (RA 3 Lee 
EQUIPMENT OF THE LABORATORY. 
Many pieces of apparatus may be procured from time to time, as the exigencies 
of the work demand or as the funds will permit. Other apparatus must be provided 
on the start, and some of it when the building is constructed or reconstructed. 
*Fic. 79.—Small portion of a cabbage leaf from Long Island, New York, showing characteristic 
water-pore infections due to Bacterium campestre:. ‘The blackeried veins correspond to the location 
of the bulk of the bacteria which have gained entrance to the vascular system of the leaf by way of 
the groups of water-pores situated on the serratures of the leaf, particularly those which are conspic- 
uously blackened. ‘Those parts of the leaf where only the larger veins are shown were green and 
normal in appearance. Coll. July 16, 1902. Drawn from a photograph. 
