A SYSTEMATIC AND STRUCTURAL ACCOUNT OF AVRAINVILLEA. 101 



detached after the outgrowth from it of the slender filament. In 

 the same species there are occasionally to be "met with certain 

 swollen bladder-like outgrowths from the frond-filaments. One of 

 us observed these also in the living state, and, recalling similar but 

 more definitely-developed outgrowths in the allied genus, Halimeda, 

 he kept them under observation, but without success. A minute 

 examination of a great number of living plants from different 

 localities in the West Indies, of plentiful spirit material and 

 numerous dried specimens of the species described in this paper 

 has been made without further result. 



As in the case of so many of our native Algse, these plants call 

 not only for careful examination, but for prolonged watching. One 

 individual of A. longicaulis is obviously in the position to produce 

 a number of others vegetatively by means of the rhizome-like 

 structure described. They grow commonly in large patches, and it 

 is very rare under these circumstances to find one unconnected with 

 its neighbours by this means. Strictly speaking, such a connected 

 colony of fronds is one individual. The separation of fronds and 

 stalks may account to some extent for the spread of this species, 

 but it plainly does not account wholly for its distribution, and of 

 course we have to deal with the other species, which have no such 

 rhizomes. The above observation as to the abjunction of terminal, 

 or the separation of interstitial propagating cells, may be a clue out 

 of the difficulty, but the subject of the reproduction of Avrainvillea 

 is well worth further investigation. 



Explanation of Plates. 



Plate 288. — Fig. 1. Part of a rhizome of A. longicaulis bearing one large 

 stalked frond, one stalk whicli has not yet formed a frond, and two broken 

 stalks (f natural size). 2. Eather old frond-filament of A. longicaulis, showing 

 dichotomous branching (x 90). 3. Frond-filament of A. longicaulis, showing 

 two protrusions, which are young branches (x 180). 4. Very small rhizoid of 

 A. longicaulis (seen chiefly in optical section) ; the wall is very much thickened, 

 and, at a, the thickening has produced a cross-wall ( x 540). 5. Shore filament, 

 /, attached to a dark body, d, filled with dark brown contents, apparently a bead 

 of a filament, which has become detached, and is putting out a young filament 

 (x 180). 6. Frond-filament of A. Mazei, showing basal constrictions at c 

 (X 120). 



Plate 289. — Fig. 7. Young plant of A. papuana with free frond-filaments 

 (natural size). 8. Older plant of A. papuana with well-developed frond of 

 interwoven filaments, edged with free filaments (natural size). 9. Tip of frond- 

 filament of A. papuana filled with granular protoplasm (x 250). 10. Filament 

 of same, with dark brown contents, capped with granular protoplasm (x 250). 

 11. Filament of A. papuana, showing nuclei, n, and chlorophyll-grains, ch 

 (x 250). 12. Filament of A. comosa, showing branching and constrictions, at 

 one of which there is a complete stopper, s, and at the other an incomplete 

 one, s' (x 80). 



