MELANOSPERMES. a 
fan-shaped outline. Others are tufts of simple bag-like fronds, being 
hollow within but closed at both ends, the apices being blunt or rounded, 
and the bases attenuated to a fine point, the roots of such being nothing 
more than a minute disk. In some the fronds are flat, but pinnated or 
divided by repeated forkings, while in others a distinct cylindrical stem 
throws out on each side numerous branches, some of which are hollow, 
while in other species the branches are solid. In no instance is there 
among this assemblage of plants an approach to leafy form or structure, 
as in the Delesseriew ; and in one genus only do we find a distinct midrib. 
This occurs in Haliseris, or sea-endive, a remarkably beautiful plant, in 
which the midrib is strong and wiry, the delicate membrane on each 
side being frequently found in a lacerated condition, owing to its extreme 
tenuity. 
Some of these elegant Melanosperms reflect prismatic colours, a pecu- 
liarity specially observable in Padina pavonia (Fig. 58) when seen 
growing in shallow rock pools under the influence of sunlight. This is 
due to the finely articulated hairs with which the segments of the plants 
are clothed, which decompose the rays of light and thus throw off the 
lovely glaucous tints so often described. With the exception of the Fucacew 
this is one of the most extensive orders among the Melanosperms, and 
some of the species are among the most attractive of our native alge. 
Some are of small size, though none of them are microscopic, while a few 
of the deep water species attain a length of several feet. In deep land. 
locked bays the species Asperococcus Turneri grows to a length of three 
or four feet, although the same species when found growing in rock pools 
between tide marks, rarely exceeds eight or ten inches. 
The Dictyotacew are more abundant in the warmer and more sheltered 
parts of the sea than in colder regions. The species which reach high 
northern and southern latitudes are few, while, on the contrary, they 
increase in number and luxuriance as they approach the tropics. Padina 
pavonia and some others abound in warmer climates, the former being met 
with in the Mediterranean and in the Channel Islands in great quantity, 
its northern limit being the southern shore of England. Dictyota 
dichotoma (Fig. 61) is found in all seas from the antarctic lands to the 
tropics. Haliseris and Zonaria are the only English representatives of 
the beautiful genera to which they belong, most of the others being 
natives of warmer latitudes. 
' For convenience of description, I intend to divide this order into three 
separate groups. The first of which contains plants having flat fronds, 
many of which are cleft or divided, but rarely branched. In the second, 
the fronds are cylindrical and branched. The third containing plants with 
tubular, or flat, and unbranched fronds. 
At the head of the first division of the Dictyotacee, is placed the beautiful 
species Cutleria multifida, finely represented at Fig. 56. This is a deep 
water species, and was discovered at Yarmouth by Mr. Dawson Turner in 
1804, and was dedicated by Dr. Greville to Miss Cutler, of Sidmouth, in 
