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NOTE ON A NUMERICAL SEQUENCE 
OF PLANT FAMILIES 
I n a recent number 1 of this journal a plea is put forward for a 
linear series of families of Vascular Plants. The fossil groups are 
not to be included, i.e. are not to have numbers assigned to them 
(loc. cit. p. 270) which is in harmony with the Botanical Garden 
outlook of the paper. Certain suggestions are made for the con¬ 
struction of such a series in a table, loc. cit. p. 269. As discussion 
is invited, I am venturing to make a few suggestions. A numerical 
sequence of families would certainly be useful from the point of 
view of economy of space in labelling museum specimens and living 
plants in a Botanical Garden. With a key to the family numbers, 
which Gundersen estimates at about 300, such labels, with the name 
of the species added, might be a great boon to students. Gundersen 
desires the sequence to be the result of general consideration “ some¬ 
thing like an inventory of facts which appear to have a bearing 
on family sequence.” He is aware that the characters used in deter¬ 
mining evolutionary sequence “are in nearly all cases very different 
from those by which plants are identified” and presumably would 
be prepared to have the Hydropterideae broken up and one family 
associated with Schizeaeaceae and the other with Hymenophyllaceae. 
But even then this ideal seems difficult to secure for a single 
linear series. If we omit all the fossil groups the linear series will 
run more or less at right angles to the radial series which indicate 
the evolutionary series. 
As, however, Gundersen obviously thinks the arrangement of 
the families in a numerical sequence should be on as natural a 
basis as possible I would suggest that it is of the first importance 
to determine the larger groups. In a paper in the current number 
of this journal I have discussed this question and have drawn up 
a diagram expressing the results to which I come. If this meets 
with his views let him record around the periphery of this diagram 
the 300 families to which he refers, locating them on that part of 
1 A. Gundersen, “Plant Families: A Plea for an International Sequence.” 
New Phyt. 19, p. 264. 1920. 
