TRANSACTIONS OF SECTION K. raw; 
a result of unequal or irregular chromosome distribution during meiosis. Miss 
Lutz and myself have independently shown that the mutant lata possesses 15 
chromosomes instead of 14, and with the valuable help of Miss Nesta Thomas 
I have recently shown that the same is true of semilata. We have since found 
that all individuals possessing the foliage and habit of lata or semilata contain 
15 chromosomes, even when these characters are associated with others derived 
by inheritance from their parental forms. 
Thus, in a mutating race of @. biennis from Madrid, one mutant was @. 
lata biennis, having lata foliage and biennis flowers. This plant has 15 chromo- 
somes, and must have originated through a meiotic irregularity. Again in the 
F, of @. rubricalyx x G. grandiflora two individuals appeared in one family, 
having data foliage and habit combined with rubricalyx pigmentation. This 
lata rubricalyx type also has 15 chromosomes, showing that in addition to the 
characters derived by inheritance from the cross, the lata foliage appears when- 
ever the fertilised egg contains 15 chromosomes. 
Such instances show definitely that mutation is a process which is independent 
of the recombinations of characters such as occur in hybrids. 
The source of the 15 chromosomes was shown several years ago to lie in 
occasional irregularities in the distribution of the chromosomes during reduction. 
In such cases, two pollen grains of a pollen tetrad receive eight chromosomes, 
and the other two receive six. When an egg having seven chromosomes is fer- 
tilised by a male cell from a pollen grain with eight, the resulting individual 
will have 15 chromosomes and the foliage of lata or semilata. 
The extra chromosome, which is a triplicate of a pair already present, is 
thus associated with the development of certain foliage characters in (inothera 
in the same way that the accessory chromosome, when present in duplicate is, 
in certain insects, associated with the development of female sex characters. 
This is apparently the first case in plants in which a definite relation has been 
shown to exist between a chromosome and particular external characters. 
The extra chromosome in CEnothera sometimes changes its behaviour in 
meiosis, dividing in the first instead of the second meiotic division. The same 
thing sometimes happens to one of the ordinary chromosomes. 
9. Epiphyllous Vegetation. By Professor W. H. Lane, F.R.S. 
10. The Preservation of the British Flora. By A. R. Horwoop. 
So urgent has this matter become that it is important that the Botanical 
Section of this Association should discuss the question with a view to the 
possibility of taking some preventive steps. A committee of the Association 
was appointed for this purpose, and reported in 1886 and subsequently on the 
subject. The question then turned upon the prevalence of hawking and collect- 
ing, and the results. The raison d’étre of the present communication is entirely 
different, the facts upon which it is based, derived from all parts of the British 
Isles, being then unknown. Whilst this factor is even greater to-day, there 
are indeed other causes at work on a widespread scale, which demand the atten- 
tion of all botanists, as they seriously affect that new and increasingly important 
branch of botany, ecology. At the same time, any causes affecting the status 
of species will be viewed with apprehension by those who study systematic 
botany. 
Briefly there are certain natural or artificial factors that are difficult to 
control except in special ways, and it is to solve these, and to elicit some infor- 
mation as to the extent of their effect, that this subject is introduced. 
It is established that drought now recurs in cycles. During 1911 several 
instances of the extermination of plants were communicated to the author, and 
others were personally noted. If they are to be expected every few years some 
steps should be taken to prevent their effect being disastrous. Montane and 
ericetal species are particularly susceptible. Bog-pools are also liable to be 
completely dried up. 
Drainage is a great factor in disturbing the natural vegetation of the 
country. A single instance, the Fens, suffices to show how great such an effect 
