A. B. Stout 107 



It is quite probable that a larger number of pollinations during the 

 early portion of the period of bloom, or an extension of tests over a 

 longer portion of the time of blooming, would show that plants judged 

 as self-incompatible were somewhat feebly self-compatible. The tests 

 made show that plants may be highly self-fertile, partially self-fertile, or 

 completely self-sterile from the very first date of bloom. If end- season 

 self-fertility does develop my results are in error in that plants classed 

 as self-incompatible may later have become somewhat self-compatible. 

 Apparently in chicory the entire range of variability in the self-fertility 

 of individuals is seen during the first few days of the period of bloom. 



II. Evidence that self-incompatibility may lead to certain cases 

 of embryo abortion. 



For plants of chicory that are fully self-incompatible only mere 

 rudiments of achenes develop and the entire head which is selfed becomes 

 shrivelled as is shown in 1, 2, and 3 of Plate III. The numbers 4, 5, 

 and 6 of the same plate show the well filled heads containing seeds with 

 embryos from flower heads of the same plant cross-pollinated on the same 

 day that the heads of figs. 1 and 2 were selfed. The conditions here 

 shown are typical of self-incompatibility, and are proof that (1) the sex- 

 organs are potent and capable of functioning in certain relations and 

 that (2) the plant is able to nourish embryos when there is compatible 

 fertilization. It seems clear that embryo abortion of any sort, and 

 especially that involving a condition of vegetative vigour, is not operating 

 in such extreme cases of incompatibility. 



For the feebly self-compatible plants, however, there is usually a 

 rather graded series of more or less developed but empty achenes as is 

 shown in 7 and 8 of Plate III. At a of no. 7, is a group of 14 mere 

 rudiments of achenes, at b are 5 achenes of good size but entirely 

 empty, and at c is one good achene with an embryo ; these are all from 

 a single head of a plant judged as feebly self-compatible. No. 8 shows 

 a graded series of 16 empty achenes and four good seeds, two of which 

 were crushed to determine if embryos were present. 



No. 9 shows 11 good seed, 2 empty achenes which appear externally 

 to be good seed, and 7 that are obviously shrivelled and empty. 



Thus in the partially self-fertile plants there are usually present in 

 those heads which have good seed some achenes which are considerably 

 developed but which contain no embryos at maturity. Possibly the 

 development of a few seeds has an influence on the phenospermic (using 

 term of Goodspeed, 1915) development of certain others of the head 



