180 HETEEOSXYLED TEIMOEPHIC PLANTS. Chap. IV. 



the pollen-grains from the two sets of anthers do not 

 differ in diameter. 



Some facts communicated to me by Fritz Miiller 

 afford excellent evidence of the utter sterility of one 

 of the forms of certain trimorphic species of Oxalis, 

 when growing isolated. He has seen in St. Catharina, 

 in Brazil, a large field of young sugar-cane, many 

 acres in extent, covered with the red blossoms of one 

 form alone, and these did not produce a single seed. 

 His own land is covered with the short-styled form of 

 a white-flowered trimorphic species, and this is equally 

 sterile ; but when the three forms were planted near 

 together in his garden they seeded freely. With two 

 other trimorphic species he finds that isolated plants 

 are always sterile. 



Fritz Muller formerly believed that a species of 

 Oxalis, which is so abundant in St. Catharina that it 

 borders the roads for miles, was dimorphic instead of 

 trimorphic. Although the pistils and stamens vary 

 greatly in length, as was evident in some specimens 

 sent to me, yet the plants can be divided into two 

 sets, according to the lengths of these organs. A 

 large proportion of the anthers are of a white colour 

 and quite destitute of pollen ; others which are pale 

 yellow contain many bad with some good grains ; and 

 others again which are bright yellow have apparently 

 sound pollen ; but he has never succeeded in finding 

 any fruit on this species. The stamens in some of 

 the flowers are partially converted into petals. Fritz 

 Muller after reading my description, hereafter to be 

 given, of the illegitimate offspring of various hetero- 

 styled species, suspects that these plants of Oxalis 

 may be the variable and sterile offspring of a single 

 form of some trimorphic species, perhaps accidentally 

 introduced into the district, which has since been 



