SAP DENSITY AND FREEZING POINTS OF LEAVES. 107 
each day is recorded at the upper edge of the diagram, and 
the precipitation, if any, underneath the word “cloudy,” 
“partly cloudy,” etc., the precipitation for clear days being 
zero. The upper line is for the maximum, and the 
lower for the minimum temperature. It will be seen from 
the diagram that during a period of clear weather the 
temperature gradually rose until reaching the 72° mark, 
dropping from here to 28° the next night, and to the mini- 
mum of 25° the following night—the greatest drop for 
any 24-hour period being 44°. It is quite probable that 
the drop just referred to, was the one that did the greater 
part of the damage, although it is quite certain that the 
next two days of freezing, with the minimum at 25°, could 
leave but little to be desired for a good freezing test. 
Furthermore, the extent of the freeze was quite general 
over the entire state, and from no section was complete 
immunity recorded. 
Foliar conditions in the main paralleled those of the 
weather. During the month of March conditions, except 
those of moisture, were very favorable for foliage growth. 
In spite of this, foliar growth was far in advance of the 
season. It would be difficult to show specifically the prog- 
ress that vegetation had made, for it would be easier to 
tell what had not as yet started, but even this would not 
be possible, because all trees had leafed out somewhat. The 
stage of leafing is, then, merely one of degree. Syringa 
vulgaris had flowered, while at the same time Catalpa was 
still in the cluster or bunched condition, while Sambucus 
canadensis must have barely started. However, for deter- 
mining the identical stages of growth in subsequent years 
the leaves of the Norway maple and the stage of growth of 
the Syringa may be taken as standards. Both of these were 
in full leaf. 
The foliage of the trees immediately after the freeze pre- 
sented an appearance that suggested fire. The northwest 
side of the trees was badly frozen in all cases, even on the 
evidently hardy material. Blackened, shapeless leaves, which 
