The Vast Majority of land plants have Eusporangia!

Homosporous Sporangia initially occurred at the Tips of the Largest Stems. These stems were unspecialized and were responsible for Photosynthesis as well as Sporangium formation. (Hepatophyta, Bryophyta, Rhyniophyta)

Homosporous Sporangia occurred at the Tips of Small Stems. The small stems had a minor role in whole-plant Photosynthesis. They were thus specialized for reproduction. (Psilophyta, Sphenophyta [Equisetum])
Homosporous Sporangia became associated with Leaves. Vegetative leaves and Sporophylls could be unspecialized and have the same morphology (Lycophyta [Lycopodium], Pterophyta) or they could be specialized for reproduction and occur in Cones (Lycophyta) or other specialized structures (Pterophyta).

Heterosporous Sporangia arose. These are generally associated with Leaves  (Lycophyta [Selaginella], Coniferophyta, Anthophyta). The Sporophylls are highly specialized for reproduction and perform little photosynthesis.

Microsporophylls & Megasporophylls occur in Cones (Lycophyta [Selaginella], Coniferophyta) or are part of the Flower (Anthophyta). The Flower is a highly modified branch with little internodal elongation. Consequently it is analogous to a Cone.

Microsporangia are exposed to the atmosphere.

Megasporangia become internal due to the growth of an enveloping  Integument. This produces the Ovule (Coniferophyta, Magnoliophyta).

The Ovule is retained by the Sporophyte throughout the entire process of Fertilization and Embryo Development. This produces Seeds.

The Ovules in Anthophyta are produced inside the Ovaries of Carpels. The Ovary forms the Fruit.

NOTE That TREND

Note the Trend from Sporangia on Stems to Sporangia on Leaves.

Note the Trend from Individual Sporangia to Grouped or Fused Sporangia.

Note the Trend from individual Sporophylls to Cones. The Flower is similar to a Cone.

Note the Trend from External Sporangia to Enclosed Sporangia (the Ovule).

Link to Importance of Ovules & Flowers

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