60 AMERICAN JOURNAL OF BOTANY [Vol. 10, 



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 I. 



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 



