94 Self- Incompatibility in Hermaphrodite Plants 



incompatible species. In the species in which it is found it occurs 

 together with variations that operate from the first day of bloom. 



Verbascum phoeniceum. 



The habit of growth in this species is especially favourable for the 

 study in question. Flowering begins when the plants are still in 

 vigorous vegetative condition. The flowers are borne on loose racemes 

 which make 'most of their growth after the first and lowermost flowers 

 bloom. The rosette leaves begin to die during the flowering period, 

 are usually dead at the end of the period of bloom, and the stems and 

 their leaves, and often the whole plant, die at the maturity of fruit. 

 The most terminal flowers usually fail to develop, obviously because of 

 waning vigour. Flowering begins when the plant is in vigorous vegeta- 

 tive condition and continues during the gradual decline in vigour and 

 the approach of death. 



The entire main raceme can be enclosed in a semi-transparent 

 " glassine " bag which can be shifted as the raceme elongates. Lateral 

 branches which bloom somewhat later than the main stem may be treated 

 likewise. In testing the plants pollinations were made at intervals of 

 from 2 to 5 days, as conditions admitted, throughout the entire period 

 of bloom. All pollinations were made by hand during the forenoon 

 when corollas are not wilted and the freshly opened stamens contain 

 much pollen. Flowers thus treated were properly tagged, and record 

 made in a card file which was carried in the field. Forceps used in the 

 manipulations were dipped in alcohol and the hands were washed in 

 water after each plant was worked. Under such treatment plants highly 

 self-fertile set fruit and seed throughout the entire period of bloom, and 

 compatible crosses were likewise successful. 



A series of 69 sister plants was grown in 1918 from seed of a cross 

 between two self-sterile plants. These parent plants had shown them- 

 selves self-sterile throughout the first half of their period of bloom in 

 the case of about 50 flowers self-pollinated under control. The seed was 

 sown in January 1918 and the seedlings were grown in pots until May 

 when planted in rows in the garden. Under this treatment flowering 

 began in June. The periods of bloom ranged from 16 to 39 days. The 

 number of flowers hand-pollinated per plant ranged from 45 to 244, and 

 the total number of flowers hand -pollinated was 7703. 



Two plants were highly self-compatible, 9 were feebly self-compatible 

 and 58 were completely self-incompatible. The two first mentioned 



