84 
Humphrey . — The Development of 
especially favourable conditions attaining a length of 30 mm., and as many 
as three times dichotomous within one growing season. Fig. i, Plate V, 
represents such a plant. A similar extra growth of the thallus has been 
reported by Campbell 1 for Sphaerocarpus under like conditions of light 
and moisture. Fossombronia longiseta is a monoecious species, though it is 
described by Howe 2 as sometimes developing antheridia to the exclusion 
of archegonia and vice 
versa. Further on in 
his description, however, 
he states that it is quite 
probable that, in cases 
where the plants are 
perennial, archegonia 
occur each alternate 
year. The writer’s ob- 
servations extend over 
two consecutive years, 
and verify Howe’s state- 
ment, though even here 
there is considerable 
variation. Plants grow- 
ing under most favour- 
able conditions of light 
and moisture quite 
regularly bear arche- 
gonia and antheridia on 
the same plant in one 
season, while those 
growing in the arbore- 
tum or in soil exposed 
to sunlight almost in- 
variably produce the 
sex- organs separately 
in alternate seasons. 
Among the Ana- 
crogynae F ossombronia 
is peculiar in that it represents something of a departure from such thallose 
forms as Aneura or Metzger ia, owing to the development of genuine leaves. 
These are disposed laterally, usually in two rows along the stem, appearing 
at first as mere outgrowths not greatly differing in appearance from the 
general structure of the young stem. But as they develop, the leaf-like 
character is unmistakable. In Text-Fig. 1, A and B represent different 
1 Campbell (’96), Fig. 9. 2 loc. cit., p. 81. 
Fig. 1. A. Young plant bearing leaves (/) and leaf-like lobes (//) 
B. A younger plant beginning to produce leaves. 
