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THE ORIGIN OF ANGIOSPERMS. 6 
out, correlated with inereased complexity of the inflorescenee ; the general 
replacement of the spiral by the cyclic arrangement in the parts of the 
flower; cohesion and adhesion, especially the evolution of the perigynous 
and epigynous states from the primitive hypogyny * ; and alterations in 
symmetry f, notably the evolution of zygomorphic structures. Further in 
many cases there has been a return to the primitive anemophilous habit, 
often accompanied by diclinism, and complicated inflorescences. 
The Andrecium. 
Perhaps the most striking contrast between the pro-anthostrobilus and the 
flower or eu-anthostrobilus, is to be found in the nature of the microsporo- 
phylls. In the Bennettitez, these are bipinnate { fronds of the fern type, 
coherent at the base, bearing greatly reduced pinnules, which in turn bear 
synangia. The connection between such organs and the andrecium of the 
Angiosperms is not at first sight obvious. If, however, we compare parallel 
stages in the evolution of the ап4гостат and the gynzceum, we may perhaps 
arrive at a clearer insight on this point. 
The seed itself is an exceedingly ancient organ, dating back far beyond the 
period at which we first became acquainted with fossil plants. In other words, 
it was a highly evolved structure at a very remote period in geological time. 
The seed of the Pteridosperms, the earliest stage in the line of descent under 
discussion with which we are at present familiar, was long antecedent to the 
evolution of the stamen. The male organs of the Pteridosperms, so far as we 
have been able to recognise them, were simple synangia-like structures, not 
dissimilar to those of the Eusporangiate Ferns in certain particulars, and 
were borne on fern-like fronds. In another Paleozoic group, the Cordaitales, 
an organ, in some respects closely similar in organisation to a stamen, existed 
contemporaneously with the fern-like male organ of the Pteridospermese, but 
this line of descent, on our view, has, at the most, only a remote connection 
with that discussed here. Thus we find that an organ in some respects like : 
stamen was in existence in the Palzozoie period, although in the Angiosperm 
line of descent it was not evolved until quite late in geological time. 
The fructifications of the Pteridospermez, both male and female, were 
borne in a lax manner, on fronds similar in structure to the sterile fronds, or 
on leaves in which the lamina was more or less greatly reduced. There is no 
indieation, in any known member of the group, that there was any attempt 
to aggregate either the male or female fructifications in the form of a 
strobilus or cone. 
* Coulter & Chamberlain (1904) p. 13. T Coulter & Chamberlain (1904) p. 15. 
1 Wieland (1906) p. 165, &c., describes the microsporophylls as “once pinnate.” They 
are, however, obviously bipinnate. 
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