FIELD MEETINGS, 1951 
Festuca altissima All. Lady Park Wood; Blackcliff. 
F. mytiros L. Railway track, near Troy Station, Monmouth (A.E.W.). 
Bromua ereclus Huds. Redding’s Inclo.snre (v.-c. 34). 
Ophioglossum vulgaturn L. Lady Park Wood. 
Azolla fUicvloides Lam. Magor. 
A. E. Wade. 
JUNE 23rd, 1951. HAULING DOWN, KENT 
Leader: Dr. R. Melville 
This meeting was arranged to give members an opportunity of study- 
ing at flowering time the same group of roses that had been examined 
in fruit at the earlier excursion of September 16th 1950. It was attended 
by 24 members and friends, but Mr. F. Rose was prevented by family 
affairs fz-om again being present as joint leader. Owing to the late 
season the roses were in good flower with the exception of Bosa spinosis- 
sima, which, as usual, was just flnishing as the majority came into bloom, 
and B. arvensis, which had not yet opened. 
Since no detailed account of the previous excursion was given it will 
be convenient, here, to describe the work of both. As a preliminary, a 
brief discussion of the cytology of the British roses was given. The 
basic chromosome number in the genus is 7, but B. arvensis is the only 
diploid (2n = 14). B. spinosissirna is a balanced tetraploid (2n = 28) and 
B. mollis an unbalanced tetraploid. The remaining species all appear to 
be pentaploids although occasional individuals may be hexaploid or have 
some other chromosome number. The znethod of reproduction is peculiar. 
The pentaploids all have haploid pollen grains (n = 7), the remaining four 
sets of chromosomes degenerating. In the egg cells, on the other hand, 
four sets of chromosomes survive azid one set degenerates. The result is 
that when fei’tilization takes place the resultant embryo is once again 
pentaploid. Similarly, in the unbalanced tetraploid, the pollen is hap- 
loid and the egg cells triploid. All except the balanced tetraploid 
jiroduce ha]doid pollen, with the obvious possibility that pollen of any 
one may fertilize the ovary of any other. Such a system of reproduc-' 
tion would allow of endless recombination of characters and appears to 
be the explanation of the gi'eat variability of our roses. Field studies 
of rose populations and the distribution of individual characters among 
the s))ecies occurring together in jzarticular habitats seem to indicate 
that this is exactly what takes place. Small wonder, therefore, that the 
I'oses form a critical group and afford us difficzzlty in their classifica- 
tion. It is much easier to criticise existing classifications, such as that 
provided in Wolley-Dod’s monograph, than to provide a good alterna- 
tive. That can only come as a result of detailed stzzdy with the pecu- 
liarities of the group kept well in mind. 
The purpose of these excursions was to point out the features charac- 
teristic of the common species, how these are distributed over tbo plant 
and how they mingle and interact in hybrids. To repi-esent a plant pro- 
|)erly in the herbarium it is necessary to have flowering shoots with 
well-developed leaves on the fertile shoots, a piece of a vegetative ex- 
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