IN VEGETATIVE AND PROPAGATIVE REGIONS 237 
But it is to be- remembered that in the ‘plant-body. the two functional 
systems, ‘the vegetative and propagative, are not equally free of one 
another. In any independent. organism the vegetative system: may increase 
. without: any-’ corresponding amplification of the propagative ; but the latter 
cannot do so without the former, since it is dependent on the vegetative 
system for its nutritive supply. In the ‘Archegoniatae this statement .will 
hold for the organism as a whole, taking gametophyte and sporophyte 
as-one. But if, as in the present. work, attention be centred. on .the 
sporophyte, : qualifications will require to be. made: for. a. considerable 
proportion of the nutritive supply of the sporophyte may originate from 
the parent gametophyte. In the embryos of all the .Archegoniatae this 
is the initial condition, and some of the simplest. have never. broken 
away from it; but in all the more advanced types the vegetation inde- 
pendence of che sporophyte is fully attained, while others hover in varying 
degree between self-nutrition and dependence. It thus becomes a question 
of the source of the nutritive supply in each separate case before it is 
possible to decide how the balance of the nutritive to the propagative 
system in the sporophyte has been adjusted in descent; and ‘this is a 
necessary preliminary to any view as to the probable amplification or 
reduction of either. 
It will be well to consider a few examples illustrative of the various 
degrees of embryonic dependence in Archegoniate Plants. In the sporo- 
gonium of /zccéa there is no self-nutritive tissue: the supply comes entirely 
from the gametophyte: it may be a question for discussion whether the 
absence of a nttritive system is due here to reduction, or is itself the 
actual primitive state; but the latter is the view usually accepted. In most 
other Liverworts there is little or no functional nutritive system in the 
sporophyte. But the Anthoceroteae form an exception, and in them it 
is represented in varying degrees: in Dendroceros and Notothylas, and 
part of the genus Axthoceros there is chlorophyll-parenchyma in the sporo-. 
gonial wall, but no stomata ; but in the two sections of the genus Anthoceros 
with non-spiral elaters, the presence of stomata is a structural indication 
of the efficiency of the sporophyte in self-nutrition. It may, however, be 
a question whether the simpler Anthoceroteae are on the upgrade or the 
down-grade of development. That a°down-grade of development may 
occur even among simple Liverworts has been placed upon a reasonable 
footing of probability by Lang, in the case of the genus Cyathodium} 
(Fig. 116), where it appears to be a consequence of growth in a moist, 
shaded habitat. Not only is the reduction effective in size, but also in 
complexity of the whole sporogonium; but the spores themselves, though 
numerically fewer, fully maintain their individual bulk. The foot is also 
reduced, and it is suggested as possible that the absence of a foot in the 
Riccia cell may be the consequence of still further reduction in them of 
a similar nature to that seen in Cyathodium. 
1 Annals of Botany, xix., p. 241. 
