Chap. III. RUBIACEiE. 135 



styled flowers, after having been soaked in water, were rather 

 larger — in about the ratio of 100 to 91— than those from the long- 

 styled flowers, and they were more triangular, with the angles 

 more prominent. As all the grains from the short-styled flowers 

 were thus characterised, and as they had been left in water for 

 three days, I am convinced that this difference in shape in the 

 two sets of grains cannot be accounted for by unequal distension 

 with water. 



Besides the several Rubiaceous genera already mentioned, 

 Fritz Miiller informs me that two or three species of Psychotria 

 and liudgea eriuntha, natives of St. Catharina, in Brazil, are 

 heterostyled, as is Manettia bicolor. I may add that I formerly 

 fertilised with their own pollen several flowers on a plant of 

 this latter species in my hothouse, but they did not set a single 

 fruit. From Wight and Arnott's description, there seems to bo 

 little doubt that Knoxia in India is heterostyled; and Asa Gray 

 is convinced that this is the case with Diodia and Spermacoce 

 in the United States. Lastly, from Mr. W. W. Bailey's descrip- 

 tion,* it appears that the Mexican Bouvardia leiantha is hetero- 

 styled. 



Altogether we now know of 17 heterostyled genera 

 in the great family of the Eubiaceae ; though moro 

 information is necessary with respect to some of them, 

 more especially those mentioned in the last para- 

 graph, before we can feel absolutely safe. In the 

 ' Genera Plantarum,' by Bentham and Hooker, tlio 

 EubiacefB are divided into 25 tribes, containing 3!5T 

 genera; and it deserves notice that the genera now 

 known to be heterostyled are not grouped in one or 

 two of these tribes, but are distributed in no less than 

 eight of them. From this fact we may infer that 

 most of the genera have acquired their heterostyled 

 structure independently of one another ; that is, they 

 have not inherited this structure from sonie one or 

 even two or three progenitors in common. It furthej 



' Bull, of (he Torrcy Bot. Club,' 1870, p. KKi. 



