I first became aware of the excellence of this cultivar years ago when I read an article about its use at Wave Hill. It's one of the viticella group hybrids, a group known for the great vigor of its members. The best known member of this group is Clematis 'Jackmanii'. The pruning of the clematis in this group is simple: in early winter cut them down to about a foot above the ground. They respond in the spring by putting up new growth which can be fifteen feet or more long. Plants pruned in this way bloom a bit later than those not pruned, but they make much more vigorous, cleaner growth.
The clematis of this group are ideal for combining with the hybrid roses derived from Rosa luciae and Rosa wichuraiana. They nearly match them in vigor, and their colors harmonize nicely. Years ago this garden boasted a huge plant of Rosa 'New Dawn' through which grew an equally robust plant of Clematis viticella: this was a great combination.
According to "The Large-Flowered Clematis Hybrids A Tentative Checklist" by J. E. Spingarn, reprinted from The National Horticultural Magazine, January, 1935 the name of this clematis is Clematis 'Madame Jules Correvon'; Spingarn attributes this variety to Lemoine, not Morel (although many other varieties are attributed by him to Morel).
For another opinion on the name, see this: