4.0. The purpose of the present section is to expand the statement of stem vowels and to list the types of phoneme sequences which occur as verb stems. Those sequences which exhibit equivalent thematic consonant alternations will then be grouped together into stem classes. A verb stem is defined as any phoneme or phoneme sequence preceded by P and followed by F. 4.1. Before proceeding with the listing of stem types and classes it will be convenient to extend the analysis of stem vowels. It was suggested in 3.1 that stem vowels a, o, e, u might be analyzed as vowel a plus a following vowel, i.e. a + a = , a + i = e, a + u = o, a + o = u. There is considerable support for this analysis of stem vowels. A sample of approximately nine hundred verbs shows that less than 4 per cent have stem vowels o, u, e, and slightly more than 6 per cent have stem vowel a, while 90 per cent are divided almost equally between a and overriding i. The regular alternation of a + a = a was noted in 2.2.1. It is now seen that stem vowel a is replaced by a when