6o 
AMERICAN JOURNAL OF BOTANY 
[Vol. io. 
in figure i, the raceme being about three feet in length. Lateral branches 
are similar but frequently somewhat shorter. It is to be noted that the 
pods are in groups separated by sections of the stem upon which no fruit 
was formed. Fruit formation is therefore decidedly intermittent. 
This habit of producing fruit intermittently was observed by the writer 
in groups of plants grown in ornamental planting in the Botanical Garden 
during previous years. For the purpose of making special observations on 
the conditions involved in the intermittent production of fruit, a crop of 
128 plants was grown in 1921. These plants were examined frequently 
throughout the entire period of bloom, and records were taken for each 
individual plant as to the character of the flowers opening at a particular 
time. At the end of the season, observations on the distribution of fruit 
in regard to the record for the flowers was made. Controlled self- and 
cross-pollinations were made on many plants. 
Every one of the 128 plants produced many pods and the seeds were 
numerous, but without exception there was decided intermittency in the 
production of fruit. On several plants there was considerable irregularity 
in the distribution of pods, but for most plants the pods were in several 
groups quite as shown in figure 1. 
The study of the flowers from day to day together with the results of 
controlled pollination showed that the intermittent production of fruit is 
due to repeated cyclic changes in the morphological character of the flowers, 
which in the course of the cycles give many grades of intersexes. The 
flowers of any individual plant varied from perfect or fully hermaphroditic 
flowers to flowers that were functional only as males or only as females, 
with also innumerable intergrades as to the relative abortion of pistils or 
stamens. As a rule, however, the loss of sex is decidedly one-sided. When 
the flowers are hermaphroditic or are female, fruit is produced provided 
pollination is accomplished; when the flowers are male only, no fruit is 
produced. The plants pass through alternating periods when the flowers 
are predominantly hermaphroditic or are female, during which they are 
productive of fruit, to periods when the flowers are predominantly or only 
male and fruitless. 
The sex character of the flowers, therefore, varies in cycles, which varia¬ 
tion makes the intermittent production of fruit a necessary result. The 
main raceme shown in figure 1 bloomed for a period of 107 days, and on 
it were produced about 250 flowers. During this time there were for this par¬ 
ticular raceme five periods when hermaphroditic and female flowers were 
produced, with intervening periods when the flowers were staminate only. 
In selecting material to illustrate these changes in sex, flowers opening 
on the same raceme at the same time were taken, the selection being made 
at a time when the variation was marked. It is, however, seldom that the 
variation on any one date represents the complete range observed for a 
plant during a complete cycle. As is shown in the figures, the sex organs 
