(30) 



antheridia, on distinct plants. Substance somewhat brittle when fresh, 

 tough and coriaceous when dry, adhering to paper when young, rather 

 imperfectly when old. Colour, a dark olive, almost black when dry. A 

 variety is common with cylindrical fronds of a pale yellow coloui'. 



This curious jjlant is one of the most common of our littoral Algse. 

 When young, the plants are densely gregariovis or even csespitose, and 

 make their first appearance like a number of minute dots, about a line 

 in diameter; these gradually elongate, squeezing each other into a 

 polygonal form, by mutual pressure, until about an inch or so in length, 

 sometimes covering a space of several square feet. We have never seen 

 them fruited in this state, but either singly or in patches of from six to 

 one or two dozen plants, so that the greater number of this dense mass 

 must be removed, possibly by extreme lateral pressure, when their 

 apices begin to expand, or by the vegetable feeding molluscs, or both. 

 When the frond has reached its fidl length, the apex becomes depressed, 

 the margin expands, and the whole assumes the form of a little cup, 

 attached to the rock by a short stalk about an inch or an inch and 

 a-half long, and the receptacle begins to protrude from the centre of the 

 cup, or in old plants from any other part of the interior, in the form 

 of a small pimple ; this rapidly elongates, forks a little above the base, 

 and becomes slightly compressed, and repeatedly divides dichotomously 

 until it reaches its full size, which some state at " twenty feet," but we 

 have never seen it above five or six. The whole of this enormous 

 receptacle is fertile, and drops off or is torn away by the force of the 

 waves when it has reached maturity, but many of the cup-shaped fronds 

 survive and produce fruit next year, perhaps repeatedly, but the recep- 

 tacles never proceed from the same point in the cup, but from some 

 other point in the interior. The cups of the first year, perhaps, only 

 produce one receptacle ; those of future years may produce several,. at all 

 events old cups are oftexi foimd with several receptacles arising from 

 different parts of the inside of the cup. 



EXPLANATION OF PLATE CXLI. 



Fig. 1. — Ilimantludia lorea, natural size. 

 2. — Portion of receptacle. 

 3. — Section of receptacle. 

 4. — Conceptacle with spores. 

 5. — Conceptacle with antheridia. 

 6.- — Spores. 

 7. — Antheridia. 

 8. — Zoospores. All magnified. 



