EUROPE AND NORTH AMERICA. 13 
appressed to the stem, and these with the spongy cuticle of the 
stem are far more effective than the roots for the transmission of 
fluid, while the dense masses formed by the aggregation of stems 
equally supersede the necessity for roots as fixing organs; these, 
therefore, being no longer needed, wither away and completely 
disappear. 
Tue STEM. 
The young stem appears from the under side of the prothallium 
by a change in the cell formation, some of the cells developing 
downwards into hair-like radicles, while the upper cell elongates 
and subdivides to form the young stemlet, some of the cells also 
becoming free laterally to form the rudimentary leaves; it is at 
first transparent, but soon acquires chlorophyl granules, and a dif- 
ferentiation into its cell layers is distinguishable at a very early 
stage. 
When the young stem has attained a height of 5 mm. it throws 
off at the sides simple flagellar branches, which arise laterally to 
the uppermost leaves, and are at first crowded in the coma and 
separate by elongation of the internodes. The branches come off 
at every fourth leaf as an obtuse bud, on which, when it has 
attained a height of three cells, 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 exten- 
sion of newly formed cells, the terminal cone thickens from above 
downward, and the base constantly forming anew attains the 
diameter of the already completed stem. 
The trunk or perfectly developed stem consists of a simple 
primary axis with numerous terminal shoots enclosing the central 
terminal bud, and also of several secondary axes; for each year a 
lateral shoot is formed beneath the growing point, which is an 
exact repetition of the original main stem, with which it keeps a 
perfectly parallel advance in growth and development ; in fact, it 
is nothing else but one of the fascicled lateral branches transformed 
into an ascending axis, and this again repeats the process the 
following season, so that we thus obtain not only the dense dicho- 
tomous ramification, but the fastigiate surface so characteristic of a 
cushion of Sphagnum plants. 
Professor Schimper in his great work described the stem as 
