Meiosis and Alternation of Generations. 213 
Perhaps it will not be inopportune to conclude this notice with 
a reference to a personal matter. 
One of the most important preliminary points which have had 
to he decided in connection with the publication of the Cambridge 
British Flora has been whether or not the arrangement of the 
families adopted by Bentham and Hooker should be retained. In 
favour of retaining this arrangement is the fact that it is the one in 
current use by botanists in all parts of the British dominions; and 
an arrangement which is so widely used cannot lightly be set aside. 
On the other hand, it has to be admitted that in almost all other 
countries, some other arrangement is in use. The arrangement in 
current use by French botanists is that of de Candolle, upon which 
Bentham’s and Hooker’s was based; and the two systems are so 
closely related, that they may, for the present purpose, be con¬ 
sidered the same; but in Germany, Switzerland, Norway, Sweden, 
the United States of America, and in several other countries, the 
newer floras are either based on Engler’s arrangement, or are on 
some plan, which, for the present purpose, may be regarded as 
nearly identical with it. What really had to be decided therefore 
was whether the Candollean system, used by French and British 
botanists, or the Englerian system, used by nearly all other 
botanists, should be adopted. Two other possibilities were seriously 
suggested : one was to follow the system of Bessey, 1 and the other 
was to modify Bentham’s and Hooker’s system in accordance with 
some modern views. 
After carefully considering the whole matter, it was decided to 
adopt Engler’s arrangement, for the reason that it is the system 
most in accord with modern views of plant affinities, and, at the 
same time, a system which is used by a large number of botanists 
of many nationalities. It is also accessible to botanists in the 
volumes of the Pfamzenfamilien , where the details of the whole 
system have been elaborated. The leading British systematists 
were consulted on the matter ; and they agreed that there was 
really no serious alternative to this plan. The way was finally 
cleared when it appeared that the late Sir J. D. Hooker, 
before his death, was prepared for the change. The disad¬ 
vantages incident to all changes will naturally be felt for some 
time by British botanists ; but in the end it will be a solid gain to 
have a British flora arranged in such a way that it can be easily 
compared with the great majority of the best floras of newer 
and other countries. 
It is not, of course, possible to undertake to adopt every 
detail of Engler’s arrangement: the right to modify details, as may 
be considered advisable, must be reserved. n R M 
Meiosis and Alternation of Generations. 
The demonstration by Lloyd Williams (1904) in Dictyota and by 
Yamanouchi (1906) in Polysiphonia that the free-living tetraspore- 
bearing plants are characterised by diploid nuclei, so that they 
could be regarded as cytologically equivalent to the “ sporophyte ” 
of the archegoniates, i.e., to the diploid phase of the life-cycle at the 
end of which meiosis occurs, marked an important epoch in the 
development of our knowledge of the relation of meiosis to alternation 
1 See Bot . Gaz ., XXIV, p. 145, 1897. 
