Article (magazine)  (Jan 1955)  Page(s) 19.  
 
The Chugai varieties imported in the 1920's and early 1930's proved to be the handsomest to reach this country. Not only that, they were true to descriptions, and re-orders brought the same variety under the same name. It is from these varieties that we had for the first time an opportunity to know what we meant when we mentioned 'Akashi-gata,' 'Dokushin-den,' 'Iro-no-seki,' or other named variety. It is unfortunate for us that the Chugai Nursery went out of business either shortly before or during World War II

Article (magazine)  (Jan 1955)  Page(s) 20.  
 
In pinks, (Class II), there are the pale 'Dokushin-den' and 'Shishinden,' and the deeper 'Iro-no-seki,' 'Doun,' and 'Terute-nishiki.'

Article (magazine)  (Jan 1955)  Page(s) 57.  
 
Alphabetical Check List of Tree Peony Names In  Public Collections And/or Available in Nurseries 1954-1955
Japanese, Pink, 'Iro-no-seki' (Barrier of Gay Color) (Jap. bef. 1893), [Gardens] Scott Foundation

Website/Catalog  (1941)  Page(s) [3].  
 
Tree Peonies
Iro-no-seki. Semi-double; flesh- and shell-pink...$4 00

Website/Catalog  (1933)  Page(s) [4].  
 
Tree Peonies - The King of Flowers
Iro-no-Seki—Semi-double, shell pink... $4.00

Website/Catalog  (1926)  Page(s) 107.  
 
Pivoines en arbre, du Japon...Iro-no-seki.- Très grande fleur rose tendre.

Website/Catalog  (1909)  Page(s) 13.  
 
Paeonia Moutan....
50. Iro-no-seki, blush large flower, 12 inches.

Website/Catalog  (1898)  Page(s) 12.  
 
Peonies.
Paeonia Mouton. Tree Peony.
This plant is already well-known to the West. Flowers in May, widely differing in color and form. Stems either shrubby or branched from the foot. The best species are native of central Japan. The flower often attains one foot in diameter. These plants have fanciful names in Japanese, which we give with as nearly as possible the English equivalent.
Double grafted set of 20, no two alike, $4.00. 1 case of 100 peonies comprising 25 varieties, $18.50.
II. Deep Crimson.
Irono-seki, Seat of Love...

Website/Catalog  (1898)  Page(s) 12.  
 
PÆONIA MOUTAN. (Tree Peonies.)
50. Iro-no-seki, blush, large flower.