CHAP. IV. OXALIS, HOMOSTYLED SPECIES. 181 



Homostyled Species of Oxalis. Although the ma- 

 jority of the species in the large genus Oxalis seem to 

 be trimorphic, some are homostyled, that is, exist under 

 a single form; for instance, the common 0. aceto- 

 sella, and according to Hildebrand two other widely 

 distributed European species, 0. stricta and corniculata. 

 Fritz Miiller also informs me that a similarly consti- 

 tuted species is found in St. Catharina, and that it ia 

 quite fertile with its own pollen when insects are ex- 

 cluded. The stigmas of 0. stricta and of another homo- 

 styled species, viz. 0. tropceoloides, commonly stand on 

 a level with the upper anthers, and both these species 

 are likewise quite fertile when insects are excluded. 



With respect to 0. acetosella, Hildebrand says that 

 in all the many specimens examined by him the pistil 

 exceeded the longer stamens in length. I procured 

 108 flowers from the same number of plants growing in 

 three distant parts of England; of these 86 had their 

 stigmas projecting considerably above, whilst 22 had 

 them nearly on a level with the upper anthers. In 

 one lot of 17 flowers from the same wood, the stigmas in 

 every flower projected fully as much above the upper 

 anthers as these stood above the lower anthers. So 

 that these plants might fairly be compared with the 

 long-styled form of a heterostyled species; and I at 

 first thought that 0. acetosella was trimorphic. But 

 the case is one merely of great variability. The 

 pollen-grains from the two sets of anthers, as observed 

 by Hildebrand and myself, do not differ in diameter. 

 I fertilised twelve flowers on several plants with pol- 

 len from a distinct plant, choosing those with pistils 

 of a different length; and 10 of these (i. e. 83 per cent.) 

 produced capsules, which contained on an average 7.9 

 seeds. Fourteen flowers were fertilised with their own 

 pollen, and 11 of these (i. e. 79 per cent.) yielded cap- 



