Sphagnales. 11 
out that in the Sphagna acutifolia and the Sphagna suhsecunda we 
get a parallel series of forms showing the various types just men¬ 
tioned, though the two groups are readily distinguished by the 
arrangement of the green and hyaline leaf-cells as seen in cross- 
section ; while the Sphagna cuspidata and the Sphagna cymbifolia 
contain representatives of about half of the “ analogous variation ” 
forms. On the other hand, the Sphagna compacta are the least 
variable types, usually growing in relatively dry places and showing 
a very limited range of biological forms, nearly all being compact, 
though squarrose and submerged forms sometimes occur in this 
group. 
The growth of a Sphagnum shoot shows a more or less marked 
annual periodicity, though in winter it is not brought to a standstill 
unless the temperature falls to freezing point. The laying-down of 
new branches at the apex proceeds during the whole period of 
active growth (spring and summer), but the elongation of the stem 
becomes arrested in late summer or early in autumn. While the 
stem is lengthening, the outermost (oldest) of the branches forming 
the cushion-like top of the plant are continually being carried 
downwards and spaced out in tufts on the stem. Among the later 
branches formed in autumn are the male and female branches, 
which may either occur on the same plant or on different plants— 
most of the British species are dioecious, but some show either con¬ 
dition quite indifferently. The male branches are formed earlier 
than the female, and are carried down on the stem as the latter 
elongates, while the female branches arise later and are found 
during winter and spring on the upper part of the plant, but later 
are carried downwards as the stem lengthens. The sexual organs 
usually mature in late autumn and winter, and may be found fully 
developed in mid-winter, even when the plants are covered by snow. 
Fertilisation usually occurs in early spring; the young sporogonia 
may be found as early as February, and the ripe capsules shed the 
spores from about July to September. 
The male branches are at first indistinguishable from the 
ordinary divergent branches of a tuft, but later they acquire a 
characteristic appearance. One or more of the branches of a tuft 
expand and become catkin-like, and above this swollen antheridium- 
bearing region taper again to a pointed tip which may continue to 
grow like an ordinary branch, giving the “ catkin ” a spindle shape. 
The leaves that protect the antheridia resemble ordinary branch- 
leaves in structure, but are usually shorter, more closely over- 
