524 MR. J. PARKIN ON THE 
inflorescences are just as derived as we believe those of the Amentacem 
to be. 
A review of the Cycadean Gymnosperms, past and present, appears, then, 
to help us little in understanding and tracing the evolution of Angiospermous 
flower-clusters, If the solitary terminal strobilus be primitive, then many 
Gymnospermous genera have departed widely from this condition ; but this 
is not surprising. Evolution tends to progress along the least specialised 
line, this remaining the most plastic. Side lines are continually being 
given off, which rapidly end blindly in the production of highly specialised 
forms, often foreshadowing features which will appear later in a higher 
group evolved, as it were, on the main line. Hence in some Gymnospermous 
side lines the strobili (flowers) may have become clustered together or 
relegated from a terminal to an axillary position, but the main line of 
descent has clung to the solitary terminal cone, from which ultimately the 
solitary terminal angiospermous flower has arisen ; and these, in their turn, 
become grouped together or placed in the axils of leaves, thus producing the 
many arrangements of inflorescence to be seen among Flowering Plants at 
the present time. 
The manner of evolution of the strobilus, and that of the anthostrobilus in 
particular, from the Pteridospermous mode of sporophyll grouping, would 
appear easier of comprehension on the assumption of the primitive nature of 
the solitary terminal strobilus, rather than on that of an axillary one or of a 
cluster. 
The evolutionary advancement of sporophyll segregation may be considered 
to have taken place in the following order :— 
(1) The production of a number of sporophylls on the main axis apart 
from the foliage, This may be considered to have occurred in the 
Pteridospermere. 
(2) The formation of a strobilus through the main axis, after producing 
a number of sporophylls, ceasing to grow. This has occurred in 
the Cycads, with the exception of the female forms of the genus 
Cycas ; also in the Bennittitales with the formation of a special 
amphisporangiate cone, the anthostrobilus. 
(3) The next step is the formation of clusters of cones or flowers— 
inflorescences, in fact. Though such aggregates do occur in 
Gymnosperms, they reach their great development and diversity 
in the Angiosperms. 
(4) The latter group show a segregation of sporophylls of a still higher 
character—viz , the compounding of inflorescences, e. g. in the 
Composite, notably the genus Echinops. 
