( 22 ) 



diately above ; between this point and the axil other two conceptacles 

 commence and proceed along the middle of the two succeeding divisions 

 to the next axil, and so on, every branch of the frond generally becom- 

 ing fertile, barren fronds being much less common than fertile ones. 

 The central portion of this conceptacle eventually becomes enlarged, 

 either in one or more portions, forming an oblong continuous or in- 

 terrupted series of more or less spherical receptacles, filled with minute 

 somewhat angular spores. Tetraspores forming well-defined spots (sori) 

 on the surface of the frond. — Miss Gifford. Structure composed of 

 two strata of cells, those forming the central portion large, roundish, 

 hexagonal, and apparently empty; those forming the surface-stratum 

 minute and colom-ed. Substance rather firm and cartilaginous, rather 

 imperfectly adhering to paper in drying, imless after steeping for some 

 time in fresh water. CoIolu-, a fine clear pink, passing into yellowish 

 green in decay. 



This beautiful species was added to the British Flora in 1847, being 

 discovered by Dr. Cocks, of Plymouth, and very soon after by the Rev. 

 W. S. Hore. Since then it has been occasionally picked up on the south 

 and south-west coasts of England, but never in any abundance, and only 

 among rejectamenta, so that its time habitat is still unknown. 



We have seen no tetraspores nor any really barren specimens. Such 

 are described as being entirely without nerve or midrib. In all our 

 .specimens conceptacles are more or less developed, and in those 

 segments where no conceptacle is apparent externally, still there is an 

 evident difference in the central cells, where they are smaller, more con- 

 densed, and somewhat coloured. This, however, may only be the 

 incipient fructification, and it would be very desirable to ascertain 

 whether the large empty cells of the centre extend the whole breadth of 

 the frond, or whether the central portion of the frond is not occupied 

 from the first with smaller, more dense, and perhaps coloured cells, in 

 some measure analogous to a midrib ; and if not, the conversion of the 

 large colom-ed cells of the centre into the minute, compact, coloured 

 cells of the conceptacle, would still be an interesting subject of inquiry. 



In our specimens the formation of the conceptacle commences with the 

 bifurcation of the frond, and its growth proceeds simultaneously with 

 the segments, terminating when these begin to widen for the formation 

 of a new fork. 



EXPLANATION OF PLATE LXXIIL 



Fig. 1. Stenogramme interrupta, natural size. — 2. Semi-section of frond. —3. Apex 

 of segment with conceptacles. — 4. Spores from same. All magnified. 



