104 Oliver. — On Physostoma elegons , Williamson , 
It is undeniable that extreme reluctance is frequently shown in inter- 
preting a given structure as a new formation, and no doubt this conservative 
attitude has much to justify it. But no one will be prepared to maintain 
that there have never been new departures involving fresh productions in 
evolutionary history, though he may incline to relegate them to a remote 
and prehistoric past. Before such a view can be seriously advanced in any 
given instance it is necessary to establish a strong case on general grounds 
that such a production is not merely useful — for that could only explain its 
survival not its origin — but that its apparition is inherently probable under 
the circumstances. 
In considering the special case of the origin of a seed-envelope we do 
well to bear in mind what commonly happens in analogous cases. Now 
where there is localized reproductive activity — especially when centred in 
organs of a more or less persistent character — nothing is more usual than to 
find associated with it great vegetative vigour involving the parts round 
about. These manifestations may take the form of sterile, sheath-like 
upgrowths or pullulations which enclose the reproductive products, or the 
whole platform upon which the latter stand may be so permeated with 
growth that the reproductive organs become overarched or immersed. 
Examples of the former method are furnished by Coleochaete , Chara , 
numerous Fungi, Red Seaweeds, Liverworts, and the arils of Angiosperms ; 
of the latter by Fucaceae, Pteridophyte prothalli with immersed archegonia, 
the perigynous and epigynous flowers of Angiosperms. 
The capacity to form such enclosures is of such wide occurrence that 
Solms-Laubach was inclined to regard it as an indication of a means at the 
disposal of the plant for reaching a continually increasing complexity of 
structure . 1 To emphasize this ‘ principle \ to which he attached importance, 
Solms-Laubach proposed for it the term ‘ cupular formation ’, or, as we 
may say encasement. Though it may be premature to attempt to define in 
terms of stimulus and response the precise sequence of events that leads up 
to encasement, it will be readily admitted that a new departure such as the 
inception of the seed habit (where provision has to be made for the increased 
nutritive drain involved by the retention of the gametophyte would be accom- 
panied by nutritive disturbances that might easily favour the appearance 
of ‘ new formations ’. Once streams of food become diverted to spots where 
reproductive bodies are to be fed, it is difficult to see how the associated 
vegetative tissues (which are usually still in an embryonic condition when 
the reproductive bodies are laid down) are to be excluded from a share of 
these supplies. If this be granted, we see that the conditions are favourable 
for encasement, whilst these encasements, if they serve a useful purpose, will 
tend to be perpetuated. 
1 Solms-Laubach, On the Fructification of Bmnettites Gibsonianus , Ann. of Bot., vol. v* 
P* 45i. 
