24 Bews. — Some General Principles of Plant Distribution as 
Tubiflorae cohort to illustrate their application to higher group??. Guppy, 
as already mentioned, has indicated how they apply in the same way to the 
Geraniales, Geraniaceae, &c. The series now to be dealt with affords an 
even better example. 
Scrophulariaceae. 
First of all, the Scrophulariaceae are a distinctly cosmopolitan family, 
though, on the whole, most frequent in temperate regions. No fewer than 
twenty-one genera have a very wide distribution over South Africa. Most 
of the genera afford examples of widespread species giving rise to rare 
endemics, &c. And we also find examples of localized genera, 7 in the 
east, 3 in the south-west, 3 in the so-called Kalahari region, and 2 in 
the western. This in itself indicates how we may apply our principles 
of distribution to the genera as well as the species, but we can do still 
better if we follow the origin and distribution of a single well-defined tribe. 
The tribe Selagineae of the Scrophulariaceae is sufficiently distinct to 
have been separated as a family by itself in the ‘ Flora Capensis \ but it only 
differs in the characters of the ovary and fruit (the latter being two-celled 
or one-celled by abortion and indehiscent or separating into two one-seeded 
nutlets). Different authors are not quite agreed as to how much should be 
included in the tribe Selagineae, but if we take it in its widest sense then 
a polygenetic and polyphyletic origin from the Scrophulariaceae is extremely 
probable. It then consists of 10 genera and about 240 species, which are 
concentrated for the most part in South Africa. There are about 20 
species in tropical Africa and one in Madagascar. There is an outlying 
genus (. Lagotis ) widely dispersed through the north temperate zone, another 
in the Mediterranean region (G lobularici) , and a single monotype in Socotra 
( 1 Cockburnia ) ( 3 ). The fact that Lagotis has been referred to the tribe 
Digitaleae by Wettstein (in Engler and Prantl) and Globularia retained 
in a distinct family (the Globulariaceae) shows that a polyphyletic origin for 
the tribe as formerly recognized has been made the grounds for breaking it 
up, but this attempt fails to give value to the marked peculiarities of the 
organs of fructification. It seems far better to recognize the Selagineae as 
a natural systematic group to which the Scrophulariaceae bears the same 
relationship as that between numerous widespread species and their deriva- 
tives as mentioned above. The widespread family A (the Scrophulariaceae) 
has given rise to a separate tribe (or another family) B, the Selagineae with 
a very restricted and at the same time discontinuous distribution. 
We now select the two genera of the Selagineae, Selago and Walafrida . 
Selago has 112'species in South Africa, 2 of which extend into the tropics. 
There are also 17 endemic species in the latter region, mostly in the hills. 
In South Africa Selago is concentrated for the most part in the south-west 
(cf. Heliophila , Oxalis , Pelargonium , Muraltia , Protea, Erica , Cliff ortia, 
and numerous other genera with a similar distribution). Walafrida is 
