22 METASPERMAE OF THE MINNESOTA VALLEY 
Examples of the Metaspermae may be selected from the great 
mass of plants which contain their seeds in a closed ‘‘ ovary.” 
better named carpellum. Such plants range in structure from 
such lower forms as Salix and Typha to the highly developed 
Orchidaceae, Umbelliferae and Compositae, including such plants 
as Listera, Myrrhis and Hieracium. 
A more definite characterisation of the Metaspermae may be 
added to the diagnostic limitation given above. 
Characters of the Metaspermae. The Metaspermae, other 
wise called Angiospermae, are those Sporophyta which produce 
constantly polymorphic species-forms, consisting of always 
bisexual, vegetatively degenerate, parasitic gametophytic 
plants and always (a) bivalent sporophytic plants, one of which 
is produced from a close-fertilised egg and develops an endo- 
sperm of the seed, while the other is produced from a cross- 
fertilised egg and develops the embryo of the seed.—which 
latter, in turn, upon the germination of the seed, normally 
resumes development and matures into a structure of high 
vegetative specialisation from which are ultimately developed, 
either one or both sizes of spores, and from these the sexual 
plants are respectively produced. The smaller spores or 
pollen-grains are produced numerously in special spore-cases 
(sporangia), aggregated upon specially modified foliar or 
axillary structures called stamens. The larger spores are 
produced severally or, more commonly, singly, in a special 
sporangium (nucellus of ovule) surrounded with indusial mem- 
branes (ovular integuments) and the sorus (ovule) thus formed 
is borne in a closed foliar or axillary structure called a pistil. Of 
this closed pouch the actual seed-bearing cavity (ovary or 
carpellum) ripens into the fruit.which is always at first a closed 
structure The seed is a ripened sorus commonly detachable 
from the structure upon which it was produced. It contains 
within the modified indusial walls (seed-cdats) two sporophytic 
plants of different valency. One, produced from an egg fertil- 
ised by the sperm nucleus from the pollen-tube, is alone termed 
theembryo The other, produced from a close-fertilised egg, is 
termed the endosperm, and is consumed by the embryo either 
during the ripening processes of the seed or during the germi- 
nating processes of the same. 
It will be interesting to see how the Archispermae or lower 
seed-plants (Gymnospermae) differ from the Metaspermae. The 
fact that seeds are such distinct, easily defined bodies, in com 
(a). Except in some Orchidaceac? 
