heterosporous's Usage Examples:

In some of the heterosporous forms (Lepidocarpon, Miadesmia) the sporangia were sometimes surrounded by an integument; and since only a single megaspore attained maturity, the structure of the megasporangium suggests a comparison with an ovule.

In the absence of direct evidence from Palaeobotany, and bearing in mind the modifications associated with adaptation to an aquatic life in other plants, the recognition of any more definite affinity for these heterosporous ferns than that indicated above appears to be inadvisable.

The spores, as in the heterosporous Pteridophyta, are of two kindsmicrospores (pollen grains) borne in microsporangia (pollen sacs) on special leaves (sporophylls) known as stamens, and macrospores (embryo-sac) borne in macrosporangia (ovules) on sporophylls known as carpels.

Selaginella is heterosporous, the megasporangia being often found towards the base of the cone.

The cones, which in some instances at least were heterosporous, presented a general resemblance to those of Lycopodium and Selaginella, a single sporangium being situated on the upper surface of each sporophyll.

A point of interest in this heterosporous genus is that the formation of the prothallus may commence before the megaspore is liberated from the sporangium.

We cannot as yet say whether these bodies represent a somewhat unusual type of fern sporangium or whether they are microsporangia: if the latter supposition is correct the plant must have been heterosporous; but we are still without evidence on this point.

-Two very distinct orders of heterosporous Filicales, the Salviniaceae and the Marsiliaceae, are included in this group.

Some Calamites were heterosporous, sporangia with microspores and megaspores being found in the same cone.

The development of the microsporangia and the contained spores (pollen -grains) P (P g is closely comparable with that of the microsporangia in Gymnosperms or heterosporous ferns.

The spores produced in each sporangium vary from very many to a single one in the case of some heterosporous forms.

Casheana, may throw some light on the origin of the heterosporous condition.