344 LYCOPODIALES 
In considering these various prothalli it is then clear that they are 
all modifications of the same conical form: that the several parts, though 
differing in proportion, have the same positions relative to one another 
and to the sexual organs which they bear, while the differences are closely 
related to the differences of circumstance and of nutrition. There is 
reason to believe that the full chlorophyll-nutrition was the primitive state 
for them ail, and the saprophytic nutrition, seen in the subterranean or 
the epiphytic types, a deriva- 
tive state. On this basis the 
cernuum-type would be recog- 
nised as relatively primitive, 
while Z. Se/ago, being less 
specialised than the aznotinum 
or phlegmaria-types, would 
approach it more nearly than 
they do. But it does not 
follow necessarily that a species 
which is recognised as primi- 
tive in respect of one prominent 
feature, is to be held as primi- 
tive in all its features. This 
apples to ZL. cernuum: it is 
true that its prothallus is green 
and assimilating, and in this 
respect probably primitive; but 
its sporophyte is a fairly 
advanced one, with definite 
strobili, and with peltate chaffy 
sporophylls strongly differen- 
tiated from the assimilating 
Fic. 131. leaves: its axis, too, shows 
Median longitudinal section throu gh a young prothallus of | an advanced condition of the 
Lycopodium Selago. b= cell; x, root hairs ; . : a 
dérmis ; =the investing tissue, stored with reserve m stele. Thus in its general 
and harbouring an endophyte ; c=the central; g=the g 
tive tissue ; a7 =archegonium ; 4=young eukered an=anthe- characters Z. cernuum cannot 
ridia beginning to develop: g4=sexual hairs. 35. (After : 
Brochmano.) yee 2 “be held as a consistent proto- 
type of the genus. But, on 
the other hand, Z. Se/ago has a prothallus little removed from the condition 
seen in L. cervuum, while in addition the sporophyte of that species has 
been seen to represent the least differentiated type in the whole genus. 
On the general sum of its characters it would accordingly take a place as 
a relatively primitive form. But its prothallus shows distinct plasticity in 
the directions along which specialisation has extended to produce the 
more extreme types: on the one hand, its subterranean specimens, with 
elongated cylindrical form, prefgure the more specialised developments of 
L. complanatum and annotinum: the compressed and flattened form 
