<Ul> <Li> In a leptosporangium, found only in ferns, development involves a single initial cell that becomes the stalk, wall, and spores within the sporangium . There are around 64 spores in a leptosporangium . </Li> <Li> In a eusporangium, characteristic of all other vascular plants and some primitive ferns, the initials are in a layer (i.e., more than one). A eusporangium is larger (hence contain more spores), and its wall is multi-layered . Although the wall may be stretched and damaged, resulting in only one cell - layer remaining . </Li> </Ul> <Li> In a leptosporangium, found only in ferns, development involves a single initial cell that becomes the stalk, wall, and spores within the sporangium . There are around 64 spores in a leptosporangium . </Li> <Li> In a eusporangium, characteristic of all other vascular plants and some primitive ferns, the initials are in a layer (i.e., more than one). A eusporangium is larger (hence contain more spores), and its wall is multi-layered . Although the wall may be stretched and damaged, resulting in only one cell - layer remaining . </Li> <P> A cluster of sporangia that have become fused in development is called a synangium . This structure is most prominent in Psilotum and Marattiaceae such as Christensenia, Danaea and Marattia . </P>

Clusters of sporangia called sori are found on the lower surface of the fronds