Transition to the High Mountains of Tropical Africa. 531 
same holds good for AnthoxantKum uivale , K. Schum., and Koeleria cristata , 
var. supina , Pilger. 
I will mention two more Cruciferae which have apparently travelled 
from Europe to the mountains of East Africa. Subularia mouticola , A. Br., 
which grows in large tufts on the Dedjen, Abyssinia, at 4,000 m., in swampy 
and at the same time stony places, was collected again by Prof. Volkens, 
and later on again by Prof. Uhlig on the Kilimanjaro, close to melting 
snow at 3,750 m. There is only one species resembling it, viz. Subularia 
aquatica , L., having a very sporadic distribution in Europe from England 
to southern Russia at the bottom and near the edge of lakes. Hiltner, in 
a careful study on these plants (Engler’s Botan. Jahrb., vii, p. 26 4), after 
having compared the external and internal structure both of the aquatic 
and terrestrial forms of aquatica from various localities, with each other 
and with 5 . mouticola of Abyssinia, sums up that vS. mouticola is not more 
different from the terrestrial form of 6*. aquatica than this from its aquatic 
form. Therefrom it is not improbable that birds of passage brought seeds 
of .S. aquatica from Europe to the higher mountains of Abyssinia, where 
a somewhat different variety was developed. It should be borne in mind, 
however, that the genus Subularia , though classified near Lepidium as a 
rule, has a very isolated position. Its distribution may have been wider in 
former times. 
A Cruciferous plant, very generally diffused in Europe, Steuophragma 
Thaliauum , (L.) Cel., is to be found in Abyssinia and on the Kilimanjaro at 
the considerable altitude of 3,300-3,500 and 3,600 m. respectively. In 
Abyssinia, on the summit of M. Bachit and M. Silke at 4,000 m., a dwarf 
form occurs which produces flowers and fruits when only 2-3 cm. in height. 
It was named Cardamiue pusilla by Hochstetter, Sisymbrium pumilio by 
Oliver. In the ‘ Hochgebirgsflora des tropischen Afrika/ I classified it as 
a variety ; at present, I should rather believe it to be only a local modifica- 
tion. The seeds of the Steuophragma Thaliauum , common throughout the 
northern temperate zone, are so minute and light, that they may be spread 
very far by winds. The species growing also on cultivated ground, it may 
even have been introduced into Abyssinia with seeds of cultivated plants. 
Even in this case it remains a remarkable feature, that it reaches to the 
sub-alpine region only in Europe, whereas it produces a dwarf form on the 
lofty summits of Abyssinia. 
Modifications of growth resembling those of A. albida are to be seen in 
Cerastium caespitosum , Gilib. (C. vulgatum , auct., C. triviale y Link). In 
every herbarium containing a large number of specimens from numerous 
localities, it is found that this species, while varying only little in hairiness 
and juncture of the sepals, has the cauline leaves now more acute, now 
more obtuse, varying, at the same time, from 0*5-5 cm * i n length, and from 
o* 3 -i *2 cm. in width. Broad-leaved forms are especially numerous from 
