Book  (1915)  Page(s) 176.  Includes photo(s).
 
Clematis. — There is no more popular hardy climber than the Clematis.  One or two should be grown in the smallest garden.  They can be used to cover any structure from a few feet to 50 feet high.  A selection of different sorts will ensure a succession of flowers from April to October. [...] There are numerous named varieties; a dozen of the best to furnish flowers from May to October are as follows:
Jackmanii, violet-purple...

Website/Catalog  (1914)  Page(s) 109.  
 
Large Flowering Clematis
Jackmanii. This variety, with its strong, healthy growth, hardy nature and rich, deep velvety-purple flowers, is the most satisfactory of its class. Blooms with astonishing profusion on shoots of the present season; should be pruned early in spring.

Website/Catalog  (1912)  Page(s) 78.  
 
Summer and Autumn Clematis.
In bloom from July to October.
These flower upon the wood of the current year's growth, and should therefore be pruned to five or six eyes.  The varieties most suitable for bedding are marked thus*.
*Jackmanii, intense violet purple; of a brilliant metallic hue...  1s. 6d

Magazine  (Aug 1910)  Page(s) 308.  
 
Association horticole lyonnaise Procès-verbal de l’Assemblée générale du samedi 16 juillet 1910...
Examen des Apports. — Sont déposés sur les tables les produits suivants : .... — Par M. F. Morel, pépiniériste, à Lyon-Vaise:  .... 3° Une collection de clématites en fleurs coupées, parmi lesquelles ; Rubella, Jackmanni, Etoile violette, Madame Furtado Heine, Vit. alba luxurians, intermedia, recta cœrulea, Mandshurica, Davidiana, coccinea.
....A M. Francisque Morel .... pour sa collection de Clématites, prime de première classe.

Magazine  (Aug 1909)  Page(s) 40-2.  
 
Origin of the Large-Flowered Clematis
Probably the most popular kind of clematis is Clematis Jackmani which is the common purple flower that we see on porches everywhere in summer.  If I were to give its pedigree now, it would only result in confusion.  The important fact is that all the large-flowered varieties of clematis, like this, are derived more or less directly from the common Virgin's bower (Clematis Viticella) of Southern Europe and what may be called the Chinese or ever-blooming clematis (C. lanuginosa), the former parent having supplied the wealth of color while the latter has contributed the great size.
[...]
The Purple Jackmani
The famous Jackmani, is a cross between Herdersonii and lanuginosa and resembles the Chinese parent in its habit, foliage, and size, also in having from four to six sepals, but its color of flower must have been derived from the European species.  Its purple is exceptionally rich and pure, and the color is much enhanced by the velvety texture.  It originated in 1858.  —W. E. Pendleton, Pennsylvania.

Website/Catalog  (1908)  Page(s) 21.  
 
CLEMATIS...Jackmanii. Velvety purple, free flowering, and the most popular variety....Each  .40, per 10  3.00

Website/Catalog  (1907)  Page(s) 65.  
 
Clematis in pots to plant out in spring and summer.
General Collection.
34 Jackmanni (Jackmanii), violet purple.

Book  (1907)  Page(s) 142, 144.  
 
One of the grandest natural species (as distinguished from garden varieties) is Clematis lanuginosa.  This produces flowers of immense size, the colour a soft lavender-blue or lilac-tinted grey, which is enriched with a tuft of reddish anthers.  This plant does not flower so freely or so continuously as to satisfy the exigent florists, and the question has arisen, What can we do to improve it?
In the year 1858 Mr. George Jackman, of the Woking Nurseries, made an endeavor to meet that question, and extraordinary results have followed therefrom.  He crossed C. lanuginosa with C. Hendersoni, and obtained two new and splendid varieties, producing flowers remarkable for their richness of colouring, their excessive profusion, and their long continuance.  Rarely in the history of practical floriculture have we seen so great a triumph accomplished at one bound.  The two new sorts were named respectively C. Jackmanni and C. rubro-violacea.  The first-named is certainly one of the most popular garden flowers known.  The other, of which we present a faithful portrait, is less popular, but not less worthy of esteem; for its flowers are exquisitely coloured and lustrous, and are produced in the most prodigal profusion- in fact, a verandah well clothed with this clematis will present during the later summer months a display of colour of the most surprising and delightful character. [...]
It is a matter of interest that hybrid clematis may be grown in beds, and in this case require to be trained over hoopsto form a low convex shield-shaped mass of green leaves and gorgeous flowers.  For this purpose the best are Jackmanni, with violet-purple flowers; Rubro-violacea, with maroon-purple flowers; Alexandra, reddish-violet; Magnifica, purple and red; Rubella, deep claret; Star of India, reddish-plum with red stripe; Tunbridgense, reddish-lilac with mauve stripe.

Book  (1906)  Page(s) 53.  
 
Principal garden varieties of Clematis:
Jackmanni type.  (July to October.)
Jackmanni... Violet-purple.

Website/Catalog  (1906)  Page(s) 69.  
 
Jackmanni, the well-known proven sort, violet-blue, is always extraordinarily faithful. 10 pieces Mk. 7.50, 100 pieces Mk. 60.-