Rose Forms as determined by their Cytological Behaviour. 167 
up to 100 per cent, of good grains, whereas in others the percentage was 
much lower. Frequently the pollen did not mature at all. 
Making the requisite allowance for the much smaller chromosome 
complement, the whole of the stages examined showed no significant 
deviation from what obtained in the preceding type. 
(c) Rosa coriifolia var. Lintoni x R. lutetiana. 
For reasons put forward in the concluding remarks (p. 177) we have 
decided that the parentage of the plant about to come under consideration 
is what we have just stated, and a further critical study of its neighbours 
made recently has sufficed to confirm our opinion. 
Buds were collected from the plant at exactly the same time as we 
made our gatherings of Rosa 
omissa , R. vubiginosa var. apri- 
corum , R. coriifolia var. Lintoni , 
R. dumetorum var. hemitricha , 
and R. lutetiana. After fixing 
the buds of the whole lot for 
the same length of time in 
portions of the same stock of 
Carnoy’s fluid they were cut, 
stained, and mounted. For some 
unknown reason, whilst the first 
four took the stain readily, we 
had the utmost difficulty in 
overcoming the capricious be- 
haviour of this rose and R. 
lutetiana towards iron-haemato- 
xylin. Even at its best it 
never took this stain like the 
rest of the roses we have mounted. 
Basing our opinion upon a number of prophases of which Text-fig. 2, e, 
is quite typical, we have no hesitation in fixing its somatic chromosome 
number at 35, and we are convinced that seven of these were obtained from 
the lutetiana parent and twenty-eight from the other. There would thus 
be brought in from the latter twenty-one, which are presumably unac- 
customed to act as homologues of others in the stages leading to the 
semitypical reduction division, and seven that were descended from 
chromosomes capable of doing so. From Rosa lutetiana came in seven of 
like character to the latter group. Naturally one would expect that the 
last two sets would be homologous to one another and be paired in the 
imperfect reduction division. 
In Text-fig. 2,/, the seven bivalents may readily be discerned lying in 
a 
& 
2«« 
'R.SjyNe'btViS 
m 
fr 
5 
d. 
•*> 
8VV 
•*»« 
(T^.loirrysitjeW foJiAX 
Rcon^ol.SJ X 
|Ya ”R 
'R.tov-iiloUa. X 
"R. L»jreWa.v>a. 
Text-fig. 2. Somatic and heterotype metaphases 
in hybrids, x 3, coo. 
