22 
F. Cavers. 
VII. ANDRE/EALES. 
[Fig. 69]. 
HIS group is represented by the single genus Andrecea, which 
is in various respects intermediate between the Sphagnales 
and the Bryales, especially in the structure and development of the 
sporogonium. There are about 100 species of Andrecea. distributed 
over the whole earth, but especially abundant in the colder 
temperate regions, though found on the higher mountains in the 
tropics. They are small plants, which creep and branch sym- 
podially, forming dark brown or black tufts, and growing especially 
on siliceous rocks in exposed places—though two New Zealand 
species grow on wet stones in streams. 
The mature stem and leaf hardly differ in structure from those 
of various Bryales. The stem tissue is practically uniform, there 
is no definite conducting strand ; the leaf usually consists of a 
single layer of cells, but in some species has a midrib. From the 
basal creeping portions of the stem there spring numerous rhizoids, 
mostly consisting of cylindrical or plate-like outgrowths, the former 
growing into the rock crevices, while the latter become applied 
closely to the rock surface. 
The sexual organs are borne in terminal groups on separate 
branches, usually on the same plant; each group is surrounded by 
a number of large involucral leaves, and among the antheridia and 
archegonia there are numerous filamentous paraphyses. The 
development of the sexual organs was worked out by Kuhn in his 
fine memoir on the genus (3), and apparently Andrecea shows close 
resemblance to the Bryales in the general characters of these 
organs. The mature antheridium has an ellipsoid body and a 
relatively long stalk, the latter consisting of two rows of cells and 
having a dilated base. 
The sporogonium of Andrecea presents a curious mixture of 
characters, some of which are peculiar to the genus, while others 
recall the structural and embryological features of the sporophytes 
of Sphagnales and of Bryales. After the formation of the transverse 
basal wall, the divisions in the hypobasal cell are irregular, but the 
epibasal cell divides at once by oblique walls which cut out a two- 
sided apical cell. According to Waldner (4), who worked out the 
early stages in detail, the apical cell cuts off, as a rule, about six 
segments on either side before further divisions occur in the 
