1 66 Blackburn and Harrison . — The S/atus of the British 
due allowance is made for the micronuclei developed after the heterotype 
division, large numbers may be present. 
However, whether the number of microspores is great or small, their 
fate is already sealed, for they all collapse. 
In view of the great theoretical importance attached to the fact an 
occurrence observed during the hybrid homotype division must be mentioned. 
In one pollen mother- cell, instead of the usual pair one giant spindle had 
been formed involving the whole of the split univalents and the bivalents. 
Thus in the late anaphase the huge array of chromosomes could be seen 
lying in two orderly groups, just as if the cell were pursuing a normal 
mitosis (see PL X, Fig. 40). Had development been allowed to proceed, 
resulting in a functional pollen grain, we should have had a gamete 
possessing all the necessary qualifications for producing a new plant, 
orthoploid in its chromosome number, but with a complement much higher 
than those of the plants from which it was generated. Further reference 
will be made to this phenomenon later. 
Finally, on account of its extreme importance, we must insist that the 
meiotic plan just traced is that displayed by a plant admitted by every 
rose student in England to be of hybrid origin. 
(b) Rosa hybrid pimpinellif olia x ( pimpinellifotia x coriifolid). 
Of the hybrid nature of this form no doubt can be entertained, and on 
grounds detailed at length in the concluding remarks we have determined 1 
that its parents are as stated above. 
As with the plant just considered, to fix its parentage and to enable 
us to comprehend fully the nature of the chromosomes to be accounted for 
in the meiotic stages, careful counts of the number of chromosomes occurring 
in the nuclei of the cells of the style were made. The numbers so obtained 
seemed to vary slightly even when the accuracy seemed guaranteed, so that 
whilst in most cells 28 chromosomes were to be made out (Text-fig. 2, c ), 
in others 29 appeared to be present. 
When seen in polar view the plates of the heterotype division (Text- fig. 
2, d) gave without exception counts of 14, indicating that, in all probability, 
there were on the plate, as in the type previously studied, 14 pairs of 
bivalents. However, views of the spindle in profile during the anaphase 
demonstrated that widely separated chromatin fragments, and even possibly 
the halves of split univalents (PI. X, Fig. 35), lay along the spindle fibres. 
Thus the interkinesis before the homotype divisions held in store few 
untypical features likely to end in abnormalities during the division, thereby 
ensuring that reasonable numbers of perfect microspores should result. 
This was reflected for the most part in the appearance of a regular tetrad 
of four nuclei. Rarely, however, five or six could be observed. Moreover, 
too, the condition of the pollen varied with the loculus, some loculi containing 
