HOMOSPORY/HETEROSPORY
What is meant by homospory and heterospory? The most obvious answer is concerned with the spores. If the spores that are produced are all alike, then the plant is said to be homosporous; if spores are produced which do not look alike and give rise to separate male and female gametophytes, then the plant is said to be heterosporous.
Use Raven 7th, p. 376-377; 8th, p. 397-398 and the following chart as aids in understanding homospory and heterospory.
| Homosporous plants | Heterosporous plants |
| Sporangia produce spores of one type only | Sporangia produce spores of two types i.e. megaspores and microspores |
| Spores develop into bisexual gametophytes each of which bears both male and reproductive structures gametophytes. |
Megaspores develop into female gametophytes bearing female reproductive structures. Microspores develop into gametophytes bearing male reproductive structures. |
| The gametophytes develop outside the spore wall. | The gametophytes develop within the spore wall. |
| Examples Psilotum, Lycopodium, and most ferns. | Examples Selaginella, a ferns, conifers, flowering plants. |
There is not as much cell and tissue differentiation in the stems and roots of lycophytes as there is in the gymnosperms and angiosperms. Xylem usually contains tracheids, but not vessels, and the inconspicuous phloem has sieve cells, but no companion cells. Also, endodermis and pericycle are found in most stems whereas they are not normally present in the stems of angiosperms.