60 PROCEEDINGS OP THE AMERICAN ACADEMY 



to the surface of the frond, and even beyond it. Some were found 

 to project beyond the surface of the frond to a distance of over 

 a quarter of an inch (about 6 mm.). These strands appear to be of 

 an adventitious nature, and may perhaps become attached to some 

 support and grow into new plants. The filaments have the power 

 of developing into branches, and this fact leads me to think that new 

 plants may be produced from the strands. I have had little oppor- 

 tunity of making observations on growing plants, and consequently 

 have not been able to verify this supposition. But the plants of 

 Tuomeya are accustomed to grow in small bunches, the individual 

 plants of which seem to be attached to one another by stolon-like 

 stems. Such outgrowths are not uncommon both in Lemanea and 

 Batrachospermum, 



In the older portions, the walls of these secondary filaments be- 

 come thickened, and the filaments themselves become so numerous as 

 completely to fill up the space between the axis and the inner portion 

 of the cylinder mentioned above. Thus we have formed a compara- 

 tively solid frond. In Figure 10 is given a camera drawing of a por- 

 tion of a section across such a frond. At a is the cross-section of the 

 internodal cell, which occupies the centre of the section. Around a 

 are seen the cross and oblique sections of the cluster of secondary 

 filaments, here labelled b, which are entwined about a. At c is repre- 

 sented the " inner peripheric stratum " of Harvey, which can be seen 

 to be portions of a ramellus, whose next portion, d, shows smaller ele- 

 ments more densely compacted together. The cells of the two outer 

 rows (e) are elongated and cylindrical, and form the " coat of monili- 

 form filaments " which Harvey refers to as the " second peripheric 

 stratum." The drawing was made from a section, which, while fresh, 

 was carefully compared with a similar section from Harvey's plant, 

 and which was found to agree with it in every respect. 



We are now ready to compare the structure of the frond of Tuomeya 

 with that of Lemanea and Batrachospermum. In all three genera, 

 the growth is from an apical cell. In Tuomeya, as we have seen, this 

 is borne on a protruding filament, which has the young ramelli clus- 

 tered about its base in the form of microscopic filaments. The same 

 is true of BatracJwspfrmum, in which the first stages of growth from 

 the apical cell are almost identical in every respect with those of 

 Tuomeya. Lemanea has apparently an entirely diflferent mode of 

 growth, although on careful study it is seen to be in accordance with 

 the same plan. A filament of Lemanea ends in a single row of two 

 or three cells, and the first lateral cells are divided off in the same 



