Invasion LandSporangia

Sporangia in the Hepatophyta & Bryophyta were located at the Tips of their Sporophytes. Their Sporangia are called "Capsules". These are Homosporous & produce many small spores which look identical.

A terminal location provides the best distribution for wind-borne Spores.

Sporangia in the Psilophyta (Psilotum) are associated with leaves but are actually produced at the tips of short stems.

Sporangia of Sphenophyta (Equisetum) occur at the tips of highly modified Stems called Sporangiophores.

These occur in Cones.

Sporangia on Stems

Sporangia on Leaves

Sporangia in the Lycophyta are produced by Leaves called Sporophylls.

In some cases Lycopodium Sporophylls resemble vegetative leaves (Isophyllous). However, some species produce terminal Cones which contain many Sporophylls that are distinct from vegetative leaves (Anisophyllous). The latter represents an advanced trait in that different parts of the plant are specialized for optimal vegetative or reproductive functions.

Species of Selaginella are Heterosporous & produce cones with Megaspores & Microspores in separate Sporangia. The Megaspore is an advanced trait that promotes the successful development of each Zygote into a free-living organism.

The Sporangia of the Eusporangiate Ferns (Ophioglossales) are formed on Leaves. In some cases the exposed sporangia have a pinnate organization along the Veins of leaves that do not have a blade (Botrychium). This structure is called the "Fertile Segment".

The Sporangia of Ophioglossum are embedded within green tissue close to the midrib of the "Fertile Segment". There is no well developed, photosynthetic leaf blade in this case.

The sporangia of Marattia are located on the lower surface of vegetative Leaves. This location is similar to the location of Sporangia for the Leptosporangiate Ferns.

Sporangia of Leptosporangiate Ferns (Filicales) occur on the lower side of the Leaf. They are frequently found in small clusters called Sori.

In the Coniferophyta Microsporangia and Megasporangia are produced in separate Cones.

The Microsporophylls are highly reduced Leaves and have no obvious vegetative functions.

The Megasporophylls are also highly modified for sexual reproduction.

The Megasporangium is enveloped by an Integument which unites it with the Sporophyte. The Megasporangium plus its Integument is called the Ovule. The Mature Ovule (a.k.a. Seed) is released at maturity.

The Ovule is an advanced trait because it connects the megagametophyte to the parent sporophyte which provides nutrients and shelter to it and the developing Embryo. The Integument becomes the Seed Coat. The Seed is also an advanced trait because it helps to insure the successful growth of each embryo into a mature plant. It may aid in Dispersal!

With the Anthophyta the Microsporangia are part of the Stamen which is a highly modified Leaf (Microsporophyll). The Microspores are produced in Microsporangia called Pollen Sacs.

The Microspore has limited Endosporic development and becomes the Microgametophyte called Pollen.

The Megasporangium forms in the Nucellus. It is part of the Ovule which is produced inside a folded Megasporophyll known as a Carpel. The Carpel is a modified Leaf.

The Angiosperm Ovule differs from Gymnosperm Ovules in that it has two Integuments and lacks Archegonia. It contains an Egg Apparatus which produces the Zygote, and a large Central Cell which is also fertilized and produces the Endosperm.

The Ovary Wall (Pericarp) produces the Fruit & the Ovules become Seeds.The Pericarp is an advanced trait because it nourishes & protects the Ovule, and it often has a role on seed dispersal.