with a deeper tinge of yellow at the base. The peculiar appearance of 
this plant is not easily conveyed by description, but when seen it plainly 
bore the stamp of an abnormal origin. 
NV. Bertolonii habitually flowers very early, coming into blossom even 
in November, in favourable seasons, and it can have only been some stray 
remainder flowers which served to fertilize or bear seed by IV. remopolensis, 
a plant which does not flower habitually before February. In this case 
we can understand how it is that, because of their distinct seasons of 
blooming, hybridization should rarely take place; but in many other 
instances it is a profound mystery why two plants which grow together, 
are visited by the same insects, and occasionally do produce hybrid 
offspring, are not constantly intercrossed. There must be both checks 
which prevent, and tendencies which favour hybridization, which exist 
unknown to us, and this I take to afford evidence of the manifold nature 
of variation in plants, which is so often present though unperceived by 
us. For it seems probable that certain individuals of a given species 
have a far greater aptitude for receiving the fertilizing influence of the 
pollen of a distinct species than others; just as there is no doubt that 
some individuals are much more fertile than others of the same species 
when treated in the ordinary way. Careful observations repeated on the 
same individuals during several consecutive seasons, with a view to 
proving the average fecundity of each, might probably give valuable 
results, tending to clear up this question. 
EXPLANATION OF PLate XC.—Fig. A 1, part of a flower cut longitu- 
dinally, of the natural size. A 2, an outer, and A 3, an inner division 
of perianth of the natural size. A 4, a transverse section of a leaf at the 
base, and A 5, at the middle, of the natural size. A 6, transverse section 
of stem of the natural size. B 1, part of a flower cut longitudinally, of 
the natural size. B 2, and B 3, outer and inner divisions of perianth of 
the natural size. B 4, stigma and part of style, magnified. B 5, 
transverse section of leaf at the middle, of the natural size. B 6, trans- 
verse section of scape, of the natural size. 
