240 Bower. — Imperfect Sporangia in certain 
But a valuable clue for decision of the case for the leafy 
sporophyte is derived from the analogy of the simpler Bryo- 
phytes. The sporogonium of Riccia , with no seta, is currently 
accepted as the most primitive type 1 . A comparison of 
successively more complex types indicates the intercalation 
of a vegetative phase, the seta, before the spores are formed. 
The same is the case in other Bryophyta, and even in Mosses 
where the seta often produces a considerable vegetative 
development for nutritive ends. Are we to assume in these 
cases that the vegetative seta, because it precedes the capsule 
in origin in the individual, preceded it also in the phylogeny ? 
We can only conclude from their comparative study that 
spore-p“oduction , which is the constant feature in them all, 
has been deferred, by a later intercalated phase. If that be 
so, then the order of appearance of the parts of the individual 
sporogonium is not an index of the order of their appearance 
in the history of the race. 
The same argument will hold for the whole plant of a Lyco- 
podium } and an interesting analogy is to be traced between 
the successive vegetative and fertile phases of a Bryophyte 
sporogonium, and of a simple Lycopod. In such a Moss as 
Funaria or Polytrichnm, the archesporium appears in longi- 
tudinal sections of young sporogonia, as a definite row of cells 
on either side of the columella. It is impossible at first to 
tell in those rows of cells the exact limit where spore- 
development will actually begin. Below that point the cells 
of the row develop sterile, above it fertile ; but in either case 
the segmentations which lead to them are the same. Passing 
to the apex, the archesporial row is continued beyond the 
extreme limit of fertility ; structurally the possibility of 
further spore-production seems to be there, but arrested. 
In the Lycopod a similar succession of phases is seen, but 
complicated by the fact that appendicular organs are borne : 
the lower sterile region may be compared as regards its 
physiological condition with the seta, though here more 
1 Goebel, Organographie, ii, pp. 321, 328. 
