50 BRITISH MARINE ALG. 
of filaments soon fall away, collectors should look for this species in April 
and May, when the spore vessels are tolerably well developed, and the 
plant is in perfection. Its colour is a brownish olive, which changes to a 
yellow green. when the plant is mounted on paper, to which it adheres 
closely in drying. 
Carpomitra Cabrere, the last in this group, is one of the rarest of our 
seaweeds, being dredged in Plymouth Sound only, and sometimes cast 
ashore off Youghal, on the Irish coast. This singular plant arises from a 
tuber-shaped root. The branches, which are numerous and irregularly 
forked, are flat, and are furnished 
with an obscure midrib. They are 
usually erect, rather narrow below, 
but gradually widen upwards, the 
terminal branchlets having blunt or 
rounded tips, others being truncated, 
or cut off, as it were. The spore 
vessel, which has a fanciful resem- 
blance to a bishop’s mitre (hence 
the generic name), is seated on the 
tip of some of the lateral branches, 
and the round oblong spores. which 
are produced within this curious 
receptacle, are attached to _ hori- 
zontal branching filaments whorled 
round an axis or central column, 
the whole forming an extremely in- 
teresting study for microscopic 
examination. Fig. 53 c, represents 
a branch with mitriform fruit vessel ; 
beside it the fruit vessel, highly 
magnified. The specific name of 
this plant is in honour of. Signor 
Cabrera, a Portuguese naturalist. 
There are several species of Carpo- 
mitra on the Australian coasts. The 
rarity of the plant on our coasts has 
been already referred to. It has 
never, so far as I am aware, been 
taken on any other British station besides the two mentioned above. 
The Dictyotacee, most of which I shall describe, are a group 
of plants of a leather-like substance, the fronds of which are spotted 
here and there with sori or groups of spores or spore vessels. ‘The surface 
of all of these plants is seen, even under a moderate magnifier, to be 
highly reticulated, the characteristic term, Dictyotacew, which signifies a 
network-like appearance, being more or less applicable to the whole order. 
Some of these plants are flat, undivided, and expand into a broad or 
Fig. 55. Sporochnus pedunculatus, 
