They look like eggs of some sort of insect. Hard to tell which one - friend or foe. You can just spray them off with the garden hose.

When you say evergreen jasmine, I'm assuming you mean Trachelospermum jasminoides - this plant is susceptible to cushion scale infestation, and that's what this is. Google Cushion Scale and select the RHS page - you do need to spray for it, and the best time is the latter half of this month. Sooty mould might occur in the meantime - it is connected with the scale insect.

Thanks so much for your help. All three plants are on the mend!

Jolly good...