272 Transactions of the 



which, when three cells high, leaves also form, and division into 

 branches takes place. The growing point of the stem is conical, its 

 terminal cell apparently subdividing in five directions, and thus 

 continually elongating the stem ; by longitudinal division and 

 transverse extension of newly-formed cells the terminal cone 

 thickens itself from above downward, and the base, constantly forming 

 anew, attains the diameter of the already completed stem. 



The rudimentary leaves are arranged in five rows on the young 

 stemlet ; the mother cell of the leaf acquires its first segmentation 

 by a septum springing laterally from the longitudinal axis and 

 perpendicular to the surface, the apical cell again dividing by a 

 septum in the opposite direction, meeting the first at an angle of 

 90°, and by repeated division of the apical cell the leaf extends, and 

 we have a simple areolation of large quadrate cells, those at the 

 margin being more elongated, and all filled with a slimy fluid, in 

 which float small pale-green chlorophyll granules, chiefly grouped 

 around the large nucleus. With the formation of the fifth leaflet, 

 however, begins that regular difi'erentiation into two constant cell 

 forms, which gives to the Sphagnum leaf its peculiar character ; 

 each of the square cells divides unequally by a septum parallel to 

 one of its walls, the larger portion is then divided, by a septum 

 parallel to the narrow sides, into two unequal cells, the larger 

 square, the others elongated ; and the leaf now consists of a system 

 of square cells, each of which is surrounded by four oblong cells. 

 In the latter, chlorophyll granules rapidly increase in number and 

 size, while the pale-green mucilage filling the larger square cells 

 disappears, and their contents become clear as water. The 

 prosenchym cells extend themselves more and more at the expense 

 of their protoplasm, and receive fibres on the interior of their 

 walls, which at first are only fragments of rings, but afterwards run 

 together into complete rings or spirals ; finally, also, small scattered 

 rings appear on the internal surface, which become thickened by 

 resorption of the included disk, and form the margins of circular 

 foramina. In the young leaves the central cells multiply and 

 extend themselves after those at the margin have ceased to do so, 

 hence the young leaf acquires a cucuUate or hooded form; the 

 process still continuing, the hood becomes split and the leaf flattens 

 out, but the apex bears evidence of this splitting in the lacerated or 

 strongly-toothed margin. 



The male flowers in Sphagnums are arranged in amentula, 

 which occupy the termination of a certain number of the divergent 

 branches, and under their covering leaves, which are somewhat 

 broader and more coloured, are concealed the antheridia. Fre- 

 quently these branches do not terminate with the flower catkin, 

 but continue their growth with the ordinary leaves, and in 

 S. rigidum and Lindhergii the flowering branch elongates and 



