HYBRIDISATION VIEWED FROM SYSTEMATIC BOTANY. 181 
HYBRIDISATION VIEWED FROM THE STANDPOINT OF 
SYSTEMATIC BOTANY. 
By R. Auten Rotrs, A.L.S., Kew. 
“Ty the year 1819,” remarks Herbert, “having for some years previous 
paid attention to the production of hybrid vegetables, .. . I was induced 
. . . to address some detailed observations on the subject to the Horti- 
cultural Society, which were published in the ‘ Transactions’ of that 
body (iv. pp. 15-50). . . . Soon after the publication of that communication 
. . . L was accosted by more than one botanist in the words, ‘I do not 
thank you for your mules,’ and other expressions of like import, under 
an impression that the intermixture of species, which had been com- 
menced and was earnestly recommended to cultivators, would confuse 
the labours of botanists, and force them to work their way through a 
wilderness of uncertainty ; whereas it was evident to myself that it would, 
on the contrary, afford a test whereby the accuracy of their distinctions 
might be more satisfactorily investigated, many of the errors of their 
systems eradicated, and its details established upon a more solid founda- 
tion, and less upon the judgment and caprice of individuals’’ (‘* Ama- 
ryllid.,’’ pp. 835, 336). A period of upwards of sixty years has since elapsed, 
during which period the practice of hybridisation has progressed by leaps 
and bounds, and with the greatest benefit to horticulture, though the 
gain to systematic botany is not yet so apparent. The fact, certainly, 
that hybrids occur in a wild state is now more or less admitted, and 
many such plants have been recognised and described ; indeed, Herbert 
himself quotes a list of no fewer than nineteen genera in which spon- 
taneous hybrids had already been recorded—which fact doubtless 
influenced his remarks—-but even at the present day there is a good deal 
of scepticism among systematic botanists on the subject, as may be seen 
from a recent controversy respecting the genus Hpilobiwm (the Willow- 
herbs). 
As long ago as 1831 Lasch recorded the occurrence of supposed 
natural hybrids in this genus, and enumerated several which he believed 
he had recognised (“ Linnza,” vi. pp. 493-497) ; while others were subse- 
quently added, until in 1884, when Haussknecht monographed the genus, 
he enumerated a list of over sixty European ones. After perusing this 
work the Rey. E. 8. Marshall collected a number of remarkable British 
forms, and sent them, with others gathered by friends, to Prof. Hauss- 
knecht for determination. This was repeated for three successive years, 
with the result that twenty-seven natural hybrids were recognised, two of 
them being new to science (“ Journ. of Bot.,” 1889, pp. 148-147 ; 1890, 
pp. 2-10; 1891, pp. 6-9). 
The correctness of Haussknecht’s views was soon challenged. The 
well-known botanist Mr. C. B. Clarke, F.R.S., wrote: ‘‘ Haussknecht’s 
. . . hybrids are altogether beyond me” (l.c., 1891, p. 228); to which 
Mr. Marshall replied that the question of hybridity was not to be “ dis- 
