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 Muller informs me
that two or three species of Psychotria and Rudgea eriantha, 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 be 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 description, it
appears that the Mexican Bouvardia leiantha is heterostyled. (3/27. 'Bulletin of
the Torrey Bot. Club' 1876 page 106.)]
Altogether we now know of 17 heterostyled genera in the great family of the
Rubiaceae; though more information is necessary with respect to some of them,
more especially those mentioned in the last paragraph, before we can feel
absolutely safe. In the 'Genera Plantarum,' by Bentham and Hooker, the Rubiaceae
are divided into 25 tribes, containing 337 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.
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