Morphology of the Spermogonia of the Rust Fungi

SUMMARY

1.	The morphology of the spermogonia of 136 species in 68 genera was studied in free-hand and microtome sections.
2.	Presence and absence of bounding structure, shape of the hymenium, position in the host tissue, and type of growth (determinate or indeterminate) are considered useful and on this basis 11 morphological types are distinguished.
3.	Within most genera, the spermogonia are constant as to morphological type. Closely related genera tend to have spermogonia of the same or related types.
4.	Differences in the position of the spermogonia in the host tissue appear less important than the other characters used in determining the relationship between genera and groups of genera.
5.	Three main lines of development of the spermogonia are suggested as follows: (1) a group characterized by a strongly convex hymenium, (2) a group characterized by a flat or nearly flat hymenium with determinate growth, and (3) a group characterized by a flat hymenium with indeterminate growth. Each line of development is considered to have diverged rather early in the history of the rust fungi.
6.	A phylogenetic line of development from Melampsoraceae to Ravenelia and then to smaller correlated genera, such as Dicheirinia, Diorchidium, Uromycladium, and Hapalophragmium, is suggested.
7.	The morphology of the spermogonia is considered useful and important to the taxonomy and phylogeny of the rust fungi.