CHAPTER XLII. 
THE VEGETATIVE SYSTEM OF VASCULAR PLANTS 
ANALYSED. 
A most effective factor in the higher development of the sporophyte is 
the continuance of apical growth. In some few cases this is absent, as 
in the sporogonium of certain Liverworts, and the development is then but 
small; or intercalary growth may intervene as in the Jungermanniaceae, 
and be continued for a long period, as in the Anthoceroteae; but in all 
the more elaborate cases, including the Mosses and all Vascular Plants, 
localised apical growth is effective, though it is usually associated with 
intercalary growth. This localised and continued apical growth is 
taken up early by the apex of the axis in the young. embryos of 
Vascular Plants, and is persistent through life: it is by reference to the 
simpler cases where it does not exist that its importance as a factor in 
the organisation of the plant-body will be duly appreciated. In presence 
of the sporophytes such,as those of the Liverworts it becomes evident 
that apical growth is not a general factor in the neutral generation: it 
seems probable that in the first instance it did not exist, and that the 
whole sporophyte owed its origin to a primary, intra-archegonial embryo- 
geny: that localised apical growth, and as a consequence continued 
embryogeny, was acquired as a secondary development, though it has 
become a dominating influence in all the more elaborate sporophytes. 
The mode of segmentation which accompanies apical growth provides 
important material for comparison, according as it is conducted with a single 
initial cell or with many, and according as the meristem is stratified or 
not. In certain cases comparison leads to the conclusion that the more 
definite segmentation with a single initial is a derivative state in the 
sporophyte, and that with several initials the more primitive. Among the 
Bryophyta there is no distinctive evidence on this point: the sporogonia 
of the Musci have as constantly a single initial cell as those of the Hepaticae 
have none. But among the Pteridophyta evidence of value comes from 
the Filicales, and also, though less clearly, from the Lycopodiales. A 
