By this time, Bentham believed that some kind of in- 
frageneric classification could be significant in understanding 
the genus. He put what he then called Siphonia elastica, S. 
brasiliensis, S. discolor, S. Spruceana and S§. pauciflora into 
one Section, characterized by a sessile, divaricate-trilobed 
stigma; into another section, he placed §. /utea and S. 
rigidifolia, with a short, attenuate style. It is now recognized 
that this classification groups together species that are not 
closely related. Bentham pointed out, however, that, prior to 
Spruce’s field studies, little was known about floral structure in 
the genus: he wrote that, although the characters ‘have been 
verified in each instance in several, and often, in many flow- 
ers .. . it remains to be seen how far they may prove constant 
when we have specimens from a greater variety of sources’. 
A second attempt to an infrageneric classification was made 
in 1858 by Baillon in his Etude générale du groupe des Euphor- 
biacées. Using the epithet Siphonia, Baillon divided the 
species then known into two Sections: Hevea and Bisiphonia. 
Pointing out that there were, among the concepts then recog- 
nized, species which were intermediate, he placed what are 
now called Hevea guianensis and its variety lutea in Section 
Hevea; what are now known as H. brasiliensis ,H. pauciflora , 
H. Spruceana, H. Benthamiana and H. rigidifolia he included 
in Bisiphonia. The former Section had an isostemonous an- 
droecium and no disk, or, at best, an inconspicuous one; the 
latter, was characterized by having a diplostemonous an- 
droecium and a more or less well developed disk. Later, in 
1864, Baillon merely enumerated seven species (unexplainably 
omitting H. guianensis) without making mention of an in- 
frageneric classification. 
Baillon’s infrageneric classification of Hevea into two 
groups, sections or series has come down to the present time, 
even though in recent years its naturalness has been questioned 
and its acceptance has been denied by most taxonomists who 
have worked on the genus during the past thirty years. 
In 1865, Mueller offered his classification of the Euphor- 
biaceae, placing the genus Hevea in Subtribe Heveeae — the 
only genus in this subtribe. He divided Hevea into two Sec- 
tions: Euhevea (equivalent to Baillon’s Section Hevea), made 
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