morphology: passive of consonant stem and capio-group

[GJCaesar]

Dear all,

I have stumbled upon something that has forced me to ask others about a possible answer.
I have studied Latin at university for five years, but I still can't come up with an answer to this question.

It might be my lack of knowledge in Latin morphology....

The passive of mittere is as follows: mittor, mitteris, mittitur, mittimur, mittimini, mittuntur.
The passive of capere is as follows: capior, caperis, capitur, capimur, capimini, capiuntur.

I don't have a book on morphology on a shelf. I am wondering why the second person has e instead of i as a vocal between the stem and the ending -ris. I was thinking it might have to do something with the initial r of -ris, but I'm not sure why.

Any thoughts on the subject are appreciated.

Kind regards,
GJCaesar

[calvinist]

Remember that unstressed i and e were not very distinguishable to begin with. I believe one of the emperors even tried to add a letter to the alphabet to cover the schwa-type sound made by unstressed i,e. There is a reference to a Chrestus by Suetonius that is possibly a misspelling of Christus, for example. What I'm getting at is it's really a spelling convention since laudaberis and laudabiris would've probably been pronounced almost identically. It probably is the presence of the r that is encouraging a slight opening of the vowel, as you said.

[Qimmik]

The same phenomenon occurs in compounds:

in+capio > incipio
in+paro > impero

Two consonants also preserve e-vocalism:

in+captus > inceptus

ad+ap-iscor >adipiscor
ad+ap-tus > adeptus

[mwh]

Hi Thomas,
With capio etc the (short) i is part of the stem, but ie (both short) is weakened to (short) e before r, as you rightly suspect (hence also infin. capere), and to (short) i in the other consonant-preceding forms. It’s phonological, not just orthographical.
Best,
Michael

[GJCaesar]

@mwh & calvinist: thanks for you thoughts! I'm glad I was on the right track after all!

@Qimmik: thanks for the added thoughts and examples. I knew that vocalism changes in compound words, but your examples were well chosen.