mild winter of 1951-52, the attacks of _Cryptodiaporthe
castanea_ (Tul.) Wehmeyer caused considerable twig blight, especially on
our crosses of _Castanea mollissimax seguini_. This is not surprising
since _C. seguini_ comes from a warmer region in China, but why these
attacks should occur during a mild winter is a puzzle. Evidently other
factors, such as the drought of the preceding fall, entered in.

Hybridization in 1951 and 1952

A total of 2400 hybrid nuts was harvested in the 1951 season and 1690 in
1952. This compares with the 1259 nuts reported for 1950. The increased
production over past years can in part be ascribed to a concentration of
the efforts on a fewer number of different crosses; while 103 were made
in 1950, the total was 77 in 1951 and 80 in 1952. The pollinations
followed the same general program in the two seasons, the emphasis being
on the Chinese x (Japanese x American) hybrids. This is our most
promising timber tree hybrid, and it seems worthwhile to test it on a
somewhat larger scale under forest conditions. Therefore, some of the
best early crosses have been repeated, new parent trees are being tried
and selected hybrids intercrossed. Back-crosses to the native chestnut
with the CxJA hybrids were made in an attempt to improve the form of the
hybrid.

Another cross which has attained some importance in the last years is
the hybrid between Japanese chestnut (forest type, from U.S.D.A.) and
S-8, the latter being a hybrid between Japanese chestnut and _C.
pumila_, the common chinquapin. This cross has a high degree of
resistance and a sufficiently good form to make it a possible timber
tree (Fig. 1). It is also a fairly good nut bearer with nuts which ripen
early, perhaps due to the influence of the chinquapin parent (Fig. 2).
Selected individuals of this hybrid were intercrossed, and some crossing
with the native chestnut was done.

In the last two seasons the total harvest from some older Chinese trees
(26 yrs.) was recorded. The best tree yielded 25.0 lbs. in 1951 and 28.2
lbs. in 1952; on other trees the yield varied between 15 to 22 lbs. The
average size of the nuts varies considerably from year to year on the
same tree. On one Japanese tree the average weight per nut was 5.6 g.
in 1951 and 14.5 g. in 1952; on a Chinese tree the same values were 7.7
g. and 15.1 g. Other trees showed a 20-40 per cent increase in the
average weight per nut in 1952 over 1951. This seems to indicate a
marke