On the right, I've carefully squeezed the fruit between my thumbnail and forefinger, and extruded the 4 ovules within. Note that the central ridge and two lateral grooves of the adaxial side of the ovules are barely discernible.

My thumbnail is ≈15mm for scale.

____________ Backstory ____________

A critical early couplet in many (often long) Phacelia keys asks about the number of ovules/seeds per ovary/fruit (e.g. see the 1st or 2nd decision steps in each of the three 'Group Keys' in the Jepson eFlora; and similarly in Munz(1973)).

A useful 'field technique' for addressing this question is:

1) Choose a ''fairly plump & far-along'' developing fruit (e.g. from near the bottom of the longest raceme available), and try to pluck it off with a decent length of pedicel attached...to help in handling it;

2) Gingerly remove a calyx lobe or two, to better expose the top of ovary to view (your eventual aim will be to force the upper-tips of the 4 valves of the ovary to burst open...by applying pressure below, at the base of the ovary);

3) Place & hold the lower half of the fruit between your thumbnail and index finger...again, with the apex of the fruit openly in view;

4) Slowly increase lateral+upward pressure of your finger(nail)s on the lower portion of the fruit by nimbly angling the tops of your index finger & thumb closer together...until the top of the ovary pops open;

6) Count the ovules! :-) You may need to gently squeeze a bit more to make sure a sufficient number are extruded.

Voilà! Now you have a decent chance of getting through one of the major roadblocks in rigorously keying a Phacelia! ;-)