36 INTRODUCTION 
ter of an inch, is reported by one author to be seven hundred feet 
in length, by another fifteen hundre feet. It is terminated by 
a lamina fifty feet long, resembling a pinnatifid leaf, each leaflet 
of which, at its point of division on the stem, expands into an 
air-vessel as large as an egg. These air-vessels sustain the 
immense frond which floats on the surface of the water, its leaf- 
lets depending in a vertical position from the stem. M. pyrifera, 
the only species, is found in the Southern oceans and on the 
Pacific coast of North America. 
Lessonia, another genus, resembles a palm-tree. It grows 
erect to a great height and has a stem like the bole of a tree. 
It branches in a forking manner and has depending from its 
branches lamine two or three feet long. The large stems from 
which the lamine have been torn by the storms, and which have 
been cast ashore on the Falkland Islands, as described by Sir 
Joseph Hooker, resemble driftwood, as they lie in piles three or 
four feet high and extending for many miles. 
Agarum and Thalassiophyllum are arctic genera, but they are 
found within our limits, the former in the North Atlantic. It 
has a simple but enormous leaf-like frond. The latter, which is 
found on the North Pacific coast, has a compound frond. Both 
are characterized by their fronds being perforated throughout 
with holes, giving them the name of sea-colander. 
