86 MISSOURI BOTANICAL GARDEN. 
In 1886, Van Tieghem and Lecomte,* after a_histo- 
logical study of the stem and leaf, decided, because of the 
stratification of the bast and the occurrence of secretion 
passages in the pith sheath and the leaf, that Lettneria may 
be placed in or at least joined to the polypetalous order 
Dipterocarpeae, its macroscopic characters being also not 
unlike those of that family except for its diclinous reduced 
flowers. More recently Heim { has reviewed its histological 
characters, and reached the conclusion that its affinities are 
rather with the group Balsamifiuae or Liquidambareae of 
Hamamelideae (likewise a polypetalous group, with which 
Van Tieghem and Lecomte had also recognized that it 
might be compared in certain respects), near which for 
both anatomical and organographic reasons he would place 
the Leitnerieae, while allowing it to retain its autonomy. 
Many botanists look on the Apetalae as only a provisional 
aggregate of orders with reduced inflorescence, which must 
be disrupted before a truly natural system of classification 
is reached; and efforts have been made from time to time 
to distribute all of these orders among the Polypetalae and 
Gamopetalae, just as single apelatous genera and species 
are universally placed in orders otherwise characterized by 
the possession of more complete flowers. This problem is 
one that may be expected to receive aid from the many 
comparative histological studies now being made, especially 
by French and German botanists, though no purely organ- 
ographic system dispensing with the Apetalae has yet met 
with more than limited approval. 
Against the approximation of the Leitnerieae to the 
Balsamifluae, may be urged the absence of secretion pas- 
sages from the liber, and the non-scalariform duct perfora- 
tions, though the floral structure suggests a possible further 
simplification of the type of this group. On the other 
hand, the absence of secretion passages from the root, the 
* Bull. Soc. Bot. de France, xxxiii. 184. 
+ C. Rend. Assoc. Frang. pour 1’Av. des Sci., 1891, i. 281; Recherches 
sur les Diptérocarpacées, Thesis, Paris, 1892, 175. 
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