Note that Budd's Flora keys genus Trientalis as having
"scale-like lower stem leaves".  Yet Flora of Alberta
keys Trientalis europaea has having "reduced leaves 
medium in size, green", not "minute, scale-like".

Note that Flora of Albert, in its description of family
Primulaceae, states that the corolla is gamopetalous 
(petals united).  However, it keys this family as having
either united or separate petals.  Budd's flora keys the
family has having united petals.  In these pictures,
the union of the petals is hard to see.

Borealis Characteristics
   - reduced leaves minute, scale-like; 
     not medium in size, green
   - principal leaves almost entirely in a whorl 
     at tip of stem
   - principal leaves lanceolate, acute or acuminate
   - pedicels shorter than the leaves

Trientalis Characteristics
   - plants perennial
   - plants erect
   - leaves not all basal
   - plants with reduced or scale-like lower stem leaves
   - upper leaves clustered near the top of the stem
   - flowers rarely in definate umbels
   - corolla white
   - petals present
   - usually with sepals, petals, and stamens in 7's
     (sometimes 6's)
   - capsule opening lengthwise

Primulaceae Characteristics
   - herbs
   - plants green or with some chlorphyll
   - plants not twining
   - plants without milky juice
   - flowers not in heads or spikes
   - flowers with two floral rings, but with petals
     wholly or partly united forming a tube or bell
   - corolla regular
   - same number of stamens as corolla lobes
   - stamens directly in front of corolla lobes; 
     NOT alternating with them
   - anthers not opening by uplifted valves
   - 1 style
   - 1 stigma
   - ovary superior, 1-loculed