80 
IOWA ACADEMY OF SCIENCES. 
tip of the shoot. They slowly enlarge and the pistil and 
floral envelops with the stamens grow out from this little 
knob or swelling. The floral envelops grow more rapidly 
than the essential organs, and so come to enclose them as 
in the mature flower buds. A single pistil is formed, and 
numerous, usually twenty, stamens are born on the calyx. 
From one to five, usually three, flower buds are formed in 
each bud. There seems never to be a flower formed at the 
tip of the growing point in the bud, that is, no terminal 
flower is formed. This has led Golf (9) to decide that the 
flower cluster is a corymb. 
By the beginning of winter the flowers are well formed, 
the calyx, corolla, stamens and pistils well differentiated. 
Plate III. The appearance of the bud at this time is repre- 
sented in Fig. d, a longitudinal section of the bud of the 
Wyant made December 8, 1908. It will be noted that the 
stamens and the pistils are well developed, the two ovules 
showing as projections from the walls of the ovary. 
It is evident that an abnormal season of weather at the 
time of the formation of these flower buds might have an 
influence on their abundance and strength as well as in 
cutting down the reserve food stored up for their use the 
next season. These abnormal conditions might arise as 
the result of drouth, defoliation, insect and fungous en- 
rnies, etc. Then again a season may be very favorable to 
woody growth, and the tree expands its energies in that 
direction rather than in the formation of flower buds. Too 
much emphasis must not be laid upon these, however, for 
Goff (9) has found that the dropping of the leaves one year 
does not seriously affect the fertility the year following, 
yet he concludes that the conditions of the previous sum- 
mer are very potent as factors in the determination of the 
formation of fruit buds and the yield. 
During the winter there is little change, the flower in 
all its parts remaining entirely dormant. That this may 
be a critical time for the flower of some varieties is very 
probable. The consensus of opinion among horticulturists 
seems to be that the winter’s cold is often the cause of a 
shortage in fruit, and the failure of many varieties to bear. 
