424 MK. 0, DARWIN OK THE ILLEaiTIMATE OFFSPRINa 



But I must here premise that I cannot give any accurate standard 

 of comparison as far as the number of the seeds is concerned; for 

 though I counted the seeds of many legitimate or ordinary plants 

 when fertilized in various ways, the number of seeds varied so 

 greatly during successive seasons that it would obviously have 

 been unfair to take a general average as the standard of com- 

 parison for illegitimate unions made during any particular season. 

 Moreover the seeds in the same capsule frequently differ so much 

 in size that it is scarcely possible to decide which ought to be 

 counted as good seed. There remains as a standard of compari- 

 son the proportional number of fertilized flowers which produce 

 capsules containing any seed. Some of the above six plants were 

 so excessively sterile during successive seasons, that no doubt 

 could be entertained on the subject, 



Pirst, for the one illegitimate short-styled plant. In the course 

 of three seasons 27 flowers were illegitimately fertilized by pollen 

 from the same plant, and they yielded only a single capsule, which 

 contained a rather high number of seeds for a union of this nature, 

 namely, 23 seeds. As a standard of comparison I must add that 

 during the same three seasons 44 flowers borne by legitimate short- 

 styled plants were self- fertilized, and yielded 26 capsules; so that 

 the fact of the 27 flowers on the illegitimate plant having produced 

 only one capsule proves how sterile it was. To show that the con- 

 ditions of life were favourable, I should here state that numerous 

 plants of this and other species of Primula all produced an abun- 

 dance of capsules whilst growing in the same soil and situation as 

 the present and following plants. The sterility in the above 

 illegitimate short-styled plant depended on both the male and 

 female organs being in a deteriorated condition. Tliis was ma- 

 nifestly the case with the pollen ; for many of the anthers were 

 shrivelled or contabescent. Nevertheless some of the anthers 

 contained pollen, with which I succeeded in fertilizing some 

 flowers on the illegitimate long-styled plants immediately to be 

 described. Pour flowers on this same short-styled plant were 

 likewise legitimately fertilized with pollen from one of the follow- 

 ing long-styled plants ; but only one capsule was produced, con- 

 taining 26 seeds ; and this is a very low number for a legitimate 



union. 



With respect to the five illegitimate long-styled plants, derived 

 from self-fertilized short-styled and long-styled parents, tlieir 

 fertility was observed during the same three years. These five 

 plants, when self-fertilized, differed considerably from each other 



