and Polyides rotundus. 9t 



very rarely atid never with certainty, three cells meet at the same 

 point, two from one side and one from the other. The absolute 

 measure was in five the following : O'lSlT^" ; 0-1196'" ; 0-1147^" ; 

 O-1205'" ; 0-0963^ giving an average of 0'1165'". Their walls 

 consist of two layers, very rarely visible in a longitudinal section 

 of the stem, as in fig. 12, but generally visible in the transverse 

 section, as in fig. 14 & 15. These two layers do not show any 

 diff'erence, are transparent, colourless, and have a greenish tinge. 

 Oenerally these long cells seem not to have any contents ; rarely 

 I observed very indistinctly defined grains in them, as in fig. 13 ; 

 but that they have contents, probably slime, is shown by the fact 

 that iodine colours their inside brown, whilst the wall exhibits a 

 light yellow tinge. Harvey says in his 'Manual,' p. 146, ''The 

 axis of the stem consists of densely packed, longitudinal, inter- 

 lacing and anastomosing filaments/' Although I have seen up- 

 wards of 100 sections, longitudinal as well as transverse ones, 

 I never observed any sort of interlacing or anastomosing, nor 

 have I seen any connexion between these perpendicular cells, 

 which are placed parallel to each other. 



I believe that we are not justified in speaking of a root in the 

 Algae, from reasons which there is no occasion to state here, but 

 I call that basal part with which an Alga is fastened, " disc of 

 fixation/' The mode of fixation and multiplying of the stems in 

 Furcellaria fastigiata is the following. A stem C, which is fixed 

 by a little disc, a, PI. VI. fig. 19, sends out one to four or more 

 horizontal, cylindrical, thin stems just above the disc of fixation. 

 The chief stem in fig. 19 has above a, four such horizontal 

 stems. These throw up at short intervals new perpendicular 

 stems, as D, E, F, B, I, H, and produce here and there a disc 

 of fixation, as at all the points marked c, and ramify often, 

 as the stem A is thrown up by a branch of a main horizontal 

 stem. The new perpendicular stems very soon send out again 

 horizontal basal stems, such as are beginning to originate on the 

 base of the perpendicular stems A and B at 'the point h, and 

 these horizontal stems form as well discs of fixation as new per- 

 pendicular stems, and so on ; but even in large plants the space 

 occupied by the discs of fixation of all stems is not larger than 

 about an inch in diameter. 



In the young, growing points of the perpendicular stems, in 

 their attenuated base, in the horizontal stems, and in the discs of 

 fixation, the cells of the inner part of the epidermal stratum and 

 the second stratum, i. e. all globose forms of cells, have disap- 

 peared, and almost all diff'erences between the different sorts of 

 cells which the stem and the receptacles show are abolished. 

 The long perpendicular cells are in the apices of the growing 

 stem, the attenuation of its base and the horizontal stem be- 



7* 



