116 THE POLYSPORANGIATE STATE : 
cases while starvation may conduce to early flowering in many Angiosperms. 
Thus the relation of nutrition to the production of sporangia is not of a 
simple character. Goebel (Organography, p. 498) speaks of other factors, 
such as intensity of light, and internal conditions or correlations, as 
influencing the production of sporophylls. Experimentally it seems easier, 
however, to convert sporophylls into foliage leaves than to make foliage 
leaves fertile. He quotes, nevertheless, the case of a Fern, allied to 
Acrostichum Blumeanum,' in which an arrest of growth of the rhizome, 
after previous good nourishment, led to production of sporangia. This is 
a result similar to that following root-pruning of fruit-trees. It reminds 
us also of the conditions found by Klebs to determine the production of 
reproductive organs in certain Algae and Fungi.? I do not suppose, 
however, that the conditions will be found to be uniform for all sporophytes, 
any more than they have been for Algae or Fungi. In any case, the 
present knowledge of the whole subject for Vascular Plants is indefinite 
and uncertain.® 
The dme of distinctive development of cells as sporogenous cells varies 
in different plants: the following tentative conclusions may be drawn from 
such differences. When in a tissue-tract the distinction between vegetative 
and sporogenous cells takes place relatively late in the individual, the 
presumption is that the distinction has been of late origin in the race. 
On this basis the conclusion has been founded in certain cases that increase 
in number of sporangia by septation has occurred. A large potential 
sporogenous tissue having a common origin is first seen; but later it 
differentiates, part becoming actually sporogenous, part remaining sterile. 
It is concluded that these late-differentiated sterile tracts were once in 
the race fertile, and that they were subsequently diverted from this previous 
condition ; in fact, that the ontogenetic development reflects the evolutionary 
history. This is exemplified in certain Angiospermic anthers, in the 
synangia of Zmestpteris, and in the partially septate sporangia of Danaea: 
the same general argument holds also for the sporangium of Jsve¢es with 
its trabeculae. In other cases where the distinctive characters of the 
sporogenous cells or cell-groups are acquired earlier, the argument for 
septation is less clear, though on grounds of comparison a similar history 
of the structure actually seen appears probable. 
The cases above mentioned involve sporangia which are closely associated 
as synangia, and they are naturally initiated simultaneously. But differences 
of the time of distinctive development of sporogenous cells may become 
more obvious in sporangia which are separate from one another, though 
in close proximity upon the part which bears them. In those types which 
comparison, as well as the Palaeontological record, points out as the 
1Raciborski, Flora, 1900, p. 25. ° Die Bedingungen der Fortpflanzung, 1896. 
3 The determining conditions have been discussed by various writers. See Diels, 
Jugendformen und Blitenreife im Pflanzenreich, Berlin, 1906, where reference is made 
to the literature on the subject. 
