372 BOTANICAL GAZETTE (JUNE 
closer to Humphrey’s description. This trouble appears to start 
in some injury to the plant, such as the breaking off of a leaf, 
or where the plants grow poorly and the outer leaves die off. 
Starting in some such way a fungus growth develops which 
gradually works down into the stem on the side from which it 
started, producing a black, decayed spot, just as described by 
Humphrey. A growth of Botrytis appears on the affected parts, 
but the vigorous growth on the soil does not appear. The 
ultimate fate of such plants depends largely on the management 
of the greenhouse. If the soil is kept dry and the temperature 
low no great loss results, but should a period of high tempera- 
ture and considerable moisture occur the plants soon “drop” in 
the characteristic manner. A trouble of this sort appears to be 
common wherever hothouse lettuce is grown. It has generally 
been ascribed to Botrytis vulgaris, largely on Humphrey’s 
authority, and the idea appears to be general that it can be held 
in check by proper handling of water and ventilation. Thus 
Humphrey says: 
It is evident that the thorough and careful culture and vigilant supervision 
of the plants are essential to the control of the disease in question... . with 
a crop well nourished and well cared for one may legitimately expect prac- 
tical freedom from loss by rotting. 
The “lettuce rot” described by Jones (2) does not appear to 
be the “drop,” although ascribed to Botrytis vulgaris. The trouble 
described by Taft (3) as caused by B. vulgaris may include the 
“drop,” but the name “mildew” is ill-chosen. Galloway (4); 
referring to the Boston soil, says: 
_ Wet rot of the lower leaves and rotting of the stems and consequent 
wilting of the plant are seldom troublesome in this soil if properly handled, 
because the surface is at all times comparatively dry. Wet rot is produced 
by Botrytis vulgaris. 
- Bailey (6) has the same idea when he says: 
This lettuce rot is due toa fungus (Botrytis vulgaris) which lives upom 
decaying matter on the soil, but when the house is kept too warm and damp, 
and the lettuce becomes flabby, it invades the plant and causes irreparable 
damage. There is no remedy, but if the soil is sandy and “sweet” and the 
