492 THE FLORA OF TROPICAL AFRICA. 
on 1ts way; indeed, owing to the delays which have interrupted its 
publication, the earlier volumes are already practically obsolete. 
How rapid has been the advance in this department of botany 
during the last half-century will be gathered from the few statistics 
now presented. 
When the late Dr. Anderson wrote his monograph, in 1862 
ho $ 
Meller, Welwitsch, Hildebrandt, Schweinfurth, Whyte, Buchanan, 
Scott Elliot, Holst and Mechow. Thanks to these and other 
explorers, the species of Thunbergia have advanced in number from 
seventeen to fifty-nine, those of Barleria from twenty-eight to 
seventy-nine, of Lepidagathis from nine to twenty-five, and so on In 
Proportion ; while Petalidiwm, in Anderson’s time scarcely known, 
and Neuracanthus, not known at all as African, are now found to 
be best represented in the «dark ’’ continent. ee 
For the earlier genera, from A ifromendoncia to Brillantatsia in- 
bulk 
laborious investigations into the pollen of these plants; and though 
Mr. Clarke is frequen ly at variance with him—more often than 
not, however, on questions merely of nomenclature—we are not 
sure t the German savant does not sometimes come out ‘ on 
top,” e.9., with regard e genus Pseudoblepharis. On the 
other hand, we think Mr. Clarke right in discarding Pseudobarleria, 
for the use of which we never could see sufficient warrant, an we 
approve his neglect of pollen characters in the case of so ‘‘natural’ 
& genus as Justicia, 
We have noticed a few—though only a few—oversighis, such 
as must inevitably occur in a work of any magnitude. Thus 
Petalidium linifolium T. And. has been omitted; the authority 
