36 AMES. 
Philippines on unreliable information or by disputable authority. Per- 
haps my enumeration is ultraconservative, but I have endeavored to make 
it accurate, exercising rather severe censorship where adequate proof 
regarding a reference was not to be obtained. 
In 1884, R. A. Rolfe* published a paper on the flora of the Philippine 
Islands and its probable derivation, in which he recorded for the Or- 
chidaceae sixty-seven genera and four hundred and sixty species. When 
it is borne in mind that my list includes ten additional genera and more 
than one hundred species which were described after Mr. Rolfe’s paper 
appeared, the discrepancy between his estimate and mine may be ac- 
counted for on the assumption that a more rigid exclusion was made on 
my part of data furnished by questionable authority. It is also possible 
that Mr. Rolfe possessed information which I have failed to secure. 
In any event it nust be conceded that estimates based on printed records 
are never conclusive and that one author may accept what another will 
reject. 
One source of error and uncertainty which it is extremely difficult to 
avoid in making provisional lists is the tendency of horticultural houses 
to conceal, for business reasons, the native country from which desirable 
orchids have been introduced. In this case species are sometimes referred 
to a region far distant from the real one, or are distributed among horti- 
culturists as natives of a country from which they may not have come. 
Although many collectors have been in the field for the Bureau of 
Science during the past five years, several horticultural orchids sup- 
posedly of Philippine origin, which would have attracted attention by 
their size and beauty, have failed to appear in the rich collections which 
have been forwarded to me for identification. The explanation of this 
may be the one offered above. If so it indicates that horticultural records 
regarding distribution should be cautiously used. 
Of the large Philippine genera which have been exhaustively studied, 
Eria and Dendrochilum occupy the foremost position. If we exclude 
Dendrobium with its fifty or more species, these two genera are the 
largest. Dendrochilum is the most interesting from a botanical view- 
point as it is the only large group which is characteristically Philippine. 
The section Acoridium, which for many years was known only through 
Dendrochilum tenellum, has grown rapidly since the botanical explora- 
tions were instituted which followed the American occupation of the 
Islands, until it now numbers over thirty species. Of these not one is 
known to be a native of any other part of the eastern Tropics and none 
so far as I have been able to ascertain has any near allies outside of the 
Philippines. When J. J. Smith monographed Dendrochilum in 1904 
only forty-three species had been described. At present more than fifty 
? Journ. Linn. Soc. Bot. 21: 283. 
