io6 
L. Cockayne 
wild hybrids of the earth should be made and its results replace the 
excellent but now obsolete monograph of Focke 1 . 
It might well be expected that the floras of different countries 
would contain descriptions of the hybrids as well as of the species, 
but this is far from being the case, the majority of such works having 
little, or nothing, to say on the subject. There has existed a feeling 
amongst taxonomists—nor is that feeling extinct by any means— 
that either wild hybrids are so few as to be negligible, or that they 
are of a low status hardly worth mentioning. Indeed certain botanists 
have doubted their existence altogether 2 . Few, apparently, have 
recognised that, as a flora is essentially an instrument for the identi¬ 
fication of any plant growing wild in the area with which it deals, 
hybrids should bear names and be described equally with species. 
This is the regular procedure in Das Pflanzenreich, Grosser, for in¬ 
stance, devoting several pages to Cistus hybrids 3 , and even supplying 
a key for their ready identification. Also, certain monographs do 
not neglect hybrids, e.g. to mention two of importance to the New 
Zealand flora, those of Haussknecht 4 and Bitter 5 . 
Unfortunately, the conclusions arrived at concerning hybrid 
origins are too frequently derived from the study of dried plants, 
whereas no really legitimate dictum can be made except one based 
on field-observations, since such alone can declare to what extent 
any suspected hybrid fulfils those conditions which, in lieu of genetic 
research, can decide, almost for certain, whether the plant in question 
be a hybrid. The following seem the principal conditions 6 and it is 
upon the fulfilment of these, subject to the exceptions cited below, 
1 Die Pflanzenmischlinge. Berlin, 1881. 
2 For example, C. B. Clarke in Jouvn. of Bot. p. 228, 1891, when criticising 
Haussknecht’s action in describing hybrids of Epilobium. 
3 Cistacece, Heft 14 ( 4 , 193), pp. 27-32. Leipzig, 1903. 
4 Monographie dev Gattung Epilobium. Jena, 1884. 
5 Die Gattung Acaena. Bibliotheca Botanica, Heft 74,1, n, hi, iv. Stuttgart, 
1910-n. 
6 See L. Diels, Die Methoden der Phytographie und der Systematik der 
Pflanzen, Handb. d. biolog. Arbeitsmethoden, Abt. 11, Teil 1, Heft 2, pp. 169-70. 
Berlin, 1921. Diels gives in addition to those below, (1) the variation is often 
of a degenerate or monstrous character, (2) the pollen grains are frequently 
misshapen or the fruits badly developed or wanting; (3) their distribution is 
irregular and the hybrid frequently absent; (4) compared with the parents 
they are few in number. 
Also, see R. A. Rolfe, Hybridisation viewed from the standpoint of Syste¬ 
matic Botany, Journ. R. Hort. Soc. (Hybrid Conference Rep.), 24 , p. 199, 1900. 
Rolfe’s conditions are much the same as mine. He also states that, “ sometimes 
the influence of one parent preponderates to such an extent that it becomes 
difficult to identify the second one ”—“ some individuals derived from the same 
two species being so dissimilar as to have been at first considered essentially 
distinct in their origin.” 
