MELANOSPERME.®. io 
infests, at short intervals, every portion of the plant. M. Leclancherii 
is found on faded fronds of the common Rhodymenia palmata, and 
the extremely minute species, M. clavatwm, occurs only on the plant 
known as Hildenbrantia rubra, a purplish-red crustaceous alga, which 
spreads over the surface of stones, and the sides of rock pools, about half- 
tide level. 
The plants included in the order Ectocarpacee, are briefly characterised 
as olive-coloured, jointed, filiform, or string-like seaweeds, whose spores are, 
for the most part, produced externally, attached to jointed ramuli or 
branchlets. The name of this order is derived from the genus Ectocarpus, 
which signifies external or exposed fruit, the fructification of all the species 
of Ectocarpus being more or less exposed or conspicuous. To those 
collectors who desire an accurate knowledge of specific distinction in this 
Fig. 75. (a) Elachista stellulata on Dictyota dichotoma. (b) Myrionema 
stvangulans on Enteromorpha compressa. (c) Myrionema punctiforme on 
Ceramium rubrum. All more or less magnified. 
genus, a microscopic examination of the fruit of these plants will prove 
at once interesting and instructive. To the unassisted eye many of the 
Ectocarpacee are wonderfully alike, but plants in fruit quickly declare 
themselves even under an ordinary lens, and when once a true species 
is secured and studied, subsequent identification, even in barren specimens 
of the same species, is thus rendered far less difficult. Many of the common 
species of this order, are very widely dispersed. The beautiful species 
Mertensii is as plentiful on some of the Scottish shores as on the south 
Devonshire coast, where, especially around Plymouth, this lovely plant 
is taken in great perfection. 
H 
