THE. ORIGIN OF ANGIOSPERMS. 69. 
spermex proper, concomitant changes! in the form and function of the 
primitive perianth may well have taken place. To the original protective 
function of this organ would be added an attractive office, in connection with 
the entomophilous habit. The changes involved may have affected the 
perianth as а whole, or only the higher series of its members. While we 
may suppose that, in some cases, the primitive perianth became differentiated 
in this way into an outer series the calyx, and an inner series the corolla, it 
is unlikely that all corollas, or, for that matter, all calyces have originated 
in this manner. The study of the homologies of the members of the floral 
envelopes among living Angiosperms is a very difficult one, as we have already 
pointed out (р. 50). In some cases, e. g, .Vymphea, the petals may be 
modified stamens, ¿. e. degraded fertile sporophylls, as Grant Allen * long ago 
suggested. In others, foliar structures, not originally forming an integral 
portion of the cone, may have come to function as a calyx. А well-known 
example occurs in the case of the involucre of Anemone Hepatica, L.f. 
While therefore, we reserve for the present a fuller discussion of the 
homologies of the various types of floral envelopes found among living 
Angiosperms, we may conclude that at least a part of the modern perianth 
was derived originally from the ancient primitive perianth of the 
Hemiangiosperms. 
The Angiospermous Tupe of Foliage. 
If our view is correct that the eu-anthostrobilus or flower of the Angio- 
sperme has been evolved from the pro-anthostrobilus of an unknown ancestor, 
allied to the Bennettitese, then we may imagine that this evolution would be 
correlated with a marked change in the habit of the whole plant, especially 
as regards the branching and leaf-form. We believe, however, that this 
latter modification took place ata considerably later geological period than 
the evolution of the flower. In other words, we conceive that the earlier 
Angiosperms may have retained, for the most part, the unbranched habit, and 
also the Cycadean type of foliage of their ancestors, for some considerable 
time after the fructification had become a typical eu-anthostrobilus or 
flower. 
One of the most difficult of the lesser problems which make up the plexus 
of problems, which we call the origin of Angiosperms, refers to the evolution 
of the typical form of Angiospermous foliage. Тһе leaves of this group are 
greatly varied both in form and size, but the majority of them exhibit 
certain peculiarities of shape and nervation, which, though hard to define, 
readily permit us to recognise at sight the affinities of such plants, even when 
we have only their detached foliage to guide us. 
* Allen (1882) p. 11. + Goebel (1905) р. 550. 
