T H E 
HEW PHYTOIiOGIST. 
Vol. XII, No. 6. June, 1913. 
[Published June 30th, 1913.] 
PHENOMENA AND PROBLEMS OF SELF-STERILITY. 
By R. H. Compton. 
U NTIL recently, perhaps no branch of Plant Physiology and 
Biology was in so obviously backward a state as the study 
of Self-Sterility. While our ignorance of the processes and causes 
of this group of phenomena is still profound, new lines of research 
have been laid open during the last few years, and there is every 
prospect of rapid accessions to our knowledge in the immediate 
future. 
I.—The Incidence of Self-Sterility. 
The facts as to the incidence of self-sterility are complex and 
baffling. It is probable that in many cases records of self-sterility 
rest on faulty observation. Some plants have been named as self- 
sterile in the absence of all evidence that pollen ever reached the 
stigma ! Other less glaring errors have arisen through the absence 
of the necessary conditions for the germination of pollen: for 
instance, Laburnum vulgare was long regarded as a typically self- 
sterile plant, for although the stigma is surrounded with pollen no 
seed is set in the absence of insects. Jost (1907), however, found 
that in this case pollen will fertilise the ovules of the same flower if 
the stigma be slightly injured by rubbing or pricking—such injury 
being produced in nature by insect visits. 
Such cases are clearly of the nature of mechanical hindrances 
to fertilization, and have nothing to do with self-sterility proper. In 
Corydalis cava also, pollen-tubes will not enter the stigma unless the 
latter be injured; but in this case there is the additional phenomenon 
of true self-sterility. In the case of pollen from the same flower the 
tubes only penetrate a very short distance into the injured stigma, 
and fail to cause fertilisation: but foreign pollen is able to produce 
tubes which grow down to the embryo-sac and bring about 
fertilisation (Jost 1907). 
