42 BOTANICAL GAZETTE [JULY 
Material when collected was placed in 70-80 per cent alcohol and 
heated to 70°C. for one hour to destroy enzymatic activity. 
The material was then extracted with alcohol and ether. The 
residue was dried and analyzed for polysaccharides, calcium, and 
oxalates. The alcohol-ether extract was evaporated to dryness on 
a steam bath and then extracted with water at 70°C. The filtrate 
of this aqueous extract was analyzed for reducing and non-reducing 
sugars; ammonia, amino acid, and nitrate nitrogen; calcium in 
solution, and acidity. 
Table IV gives a summary of an analysis of 9 different regions 
of the plant. Series C represents leaves in the act of abscissing, 
series E represents leaves at, the time of the formation of the 
abscission layer, and series D represents leaves intermediate between 
these two points. Collection Ex represents approximately 5 mm. 
of the abscission end of the petiole, collection E2 an equal portion 
of the adjacent part of the petiole, and collection Ez a portion of 
the blades. In like manner, collections C1, C2, and C3 and 
collections D1, D2, and D3 represent these same three regions in 
their respective series. 
Attention should be called to the fact that while collections 
C1, Dr, and Ex represent the abscission end of the petiole, they 
do not represent the abscission layer only. In no case does the 
abscission layer represent more than about 5 or 6 per cent of the 
portion of the petiole taken. In collection Cr it represents still 
less, probably not more than 2 per cent, as in the abscissing leaf 
the petiole retains only about one-third of the abscission layer, the 
remaining two-thirds being attached to the stem. 
It is evident that chemical changes in the abscission layer might 
be overshadowed by the remaining 95 per cent of the collection, 
and even more so in collection Cr than in collections D1 and Et. 
This is especially true of the nitrates, which are frequently confined 
almost entirely to the abscission layer and are more abundant in 
this layer at the time of abscission than at any other time, although 
the figures in the table might lead one to think they were most 
abundant a short time before abscission. As a matter of fact, a 
large percentage of the nitrates in the abscission layer of collection 
Cr were left in the part of the abscission layer remaining attached 
