184 Blackburn and Harrison . — The Status of the British 
and others, represented by Gates, by a refined extension of the crude 
notion put forward by previous writers have been inclined to see in tetra- 
ploidy and octoploidy the inciting cause. With neither of these do we 
agree. We see in our particular form of vegetative reproduction, and 
in the true apogamy of other species, a further manifestation of the powers ; 
of heterosis stimulating, in the one case cells from the soma, and in the 
other the germ-cells,* to an enormously exaggerated development ending in 
apomictical reproduction. High chromosome numbers are in this view 
merely the attendant circumstances of the hybridity and the stimulus 
induced by it. 
It needs only a glance to perceive the close analogy between the 
cytology of roses and that of other forms betraying apogamy or some kin- 
dred form of reproduction. Our roses behave exactly like Rosenberg’s 
Hieracia, Holmgren’s Eupatoria, and Ernst’s Char a crinita . In all of 
these cases, as in others, the apogamy is assigned to hybridity, and we feel 
sure that these authors are justified in the position assumed. To our minds 
apogamy and the enormous variability in Rosa and other critical genera 
like Hieracium , Taraxacum , Antennaria , and Callitriche alike take their 
origin from one and the same cause, hybridity — not set in motion now, 
but in the far distant past. 
Whatever value we assign to the various rose forms, and this, in spite . 
of their hybrid nature, cannot be assessed at less than the microgene 
or Jordanian species, their development became possible through crossing. 
Moreover, despite the vast range of variation, the centre round which 
any given microgene oscillates remains fixed ; no one, for instance, could 
ever mistake a member of the Rosa lutetiana fraternity for a R. glauca form 
and so on. Undoubtedly, therefore, hybridity has given rise to these 
recognizable, if variable, units just as to the more stable Erigeron animus , 
so that hybridity must be admitted as one of the prime factors in the 
evolution of species, if not the sole one as Lotsy would fain persuade us. 
Further, if, for example, we can imagine the egg-cell of Rosa Borreri to 
be fertilized by a pollen grain built up from the seven ‘ cap ’ chromosomes of 
R . omissa , or any other similar cross pollination, it appears far from impos- 
sible that some form of microgene building is still proceeding. If apomictical, 
as seems likely when one remembers the Lord Penzance hybrid Rubiginosae, 
the new form would be reasonably permanent from the very first. We feel 
certain that the forms arranged under Rosa subcanina , R. subcollina , and 
other groups are comparatively recent developments rendered possible 
by the northern forms belonging to the Afzelianae clashing with the more 
southern Eucaninae, possibly at the onset of the Glacial Period, whilst | 
others, like R. foetida and R. audegavensis allies, may even yet be coming 
into being. 
Lastly, we propose to consider the taxonomic value of our observations. 
