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meet here with a great difficully, if we will explain the 
origin of this second integument. Three ways are possible, 
having led to this double structure. 
À first explanation, which would be most acceptable, 
is the formation of one integument by the fusion of an 
outer and an inner one. Miss Stopes has put forwards 
this theory, as I already mentioned, when she called the 
cupule of Lagenostoma an outer integument, and the testa 
of the Cycads a double one. The objections to be made 
against her theory I have dissussed, but now I will add 
an other one, namely the fact, that if an organ once has 
been reduced or has disappeared it afterwards never comes 
back again under the same circumstances and with the 
same function. So that if two originally free whorls of 
integumental-units have fused, they lateron do not return 
to this condition by any means. Unless some fossil seeds 
become discovered, in which two distinctly separate 
integuments can be distinguished, we have to accept that 
the formation of a second envelopment is a proces of 
more recent date. 
In the second place it may be possible that a second 
whorl of organs is formed around the nucellus in the an- 
cestors of the Taxads and Gnetales. Both cycli are fused 
for the greater part amongst the Taxads, whereas they 
have remained free in Ephedra and Gnetum. Welwitschia 
with only one integument stands entirely apart, here the 
formation of a second integument has never taken place 
or it has again disappeared. 
The critic of this opinion is especially that nothing is 
known of these supposed ancestors, and no indications 
point in this direction. Besides it should be rather acci- 
dental if the organs of both cycli, always originated in 
the same number as is the case in Ephedra and Gnetum. 
Finely a third interpretation is possible, which, however, 
is not without objection either. Both integuments could 
