IX 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 the 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 Riccia 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 nutritive 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 Anthoceros 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 up-grade 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 J 

 (Fig. 1 1 6), 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 

 Riaia 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. 



