160 MR. W. B. HEMSLEY ON THE FLORA 
composition of the flora are based. A close scrutiny of the 
Kew and British Museum herbaria would probably yield a few 
additional species. 
2. Notes on the Position, Geology, and Aspects of the Vegetation 
of the Tonga Islands. By J. J. Lister, Esq., M.A. 
The Tonga or Friendly group consists of a number of small 
islands scattered along an axis whose direction is N.N.E. and 
S.S.W. The length of the group is about 200 miles. Some 
400 miles to the W.N.W. are the large islands of Fiji, and the 
Samoa islands are about 300 miles away in the direction of the 
axis northward. Tongatabou*, the largest island of the group, 
is situated at the southern end, and is about 1000 miles from 
Auckland in New Zealand. The 20th parallel of south latitude 
passes through the middle of the group. 
The group is composed in part of a line of volcanoes which 
traverses it lengthwise. Some of these are still active, while 
others are only the broken-down remnants of volcanoes which 
have been long extinct. In 1885. submarine eruption occurred, 
and a mound of ashes f was built up in the interval between two 
of the existing islands; but this has since been largely worn 
away by the sea. 
The other islands of the group are for the greater part formed 
of reef-limestone. In some of them an underlying basis is ex- 
posed, formed of volcanic tuffs laid out beneath the sea, and in a 
few cases the islands consist entirely of the latter formation. 
Movements both of elevation and subsidence have occurred, 
but the more recent tendency has been, in the main at least, one of 
elevation. Vavau, a limestone island in the northern part, is 
about 500 feet high; and Ewa, in the south, is over 1000 feet. 
Some of the voleanoes attain greater heights. The other islands 
are for the most part little elevated and flat. Generally it may 
be said that all the high ground of the group is either the summits 
of volcanoes, active or extinct, or composed of reef-limestones, 
which were, of course, formed beneath the sea. 
Soundings show that the islands are situated at the northern 
end of an extensive plateau which reaches far to the southward 
* Designated Amsterdam Island in some of the older charts.—W. B. H. 
t Falcon Island, it has been named.—W. B. H. 
