John Bangs - A Rebellious Heroine стр 6.

Then began a new quest for characters to go with Marguerite Andrews.

She must have a chaperon, to begin with, thought Harley.  That is indispensable.  Herring, Beemer, & Chadwick regard themselves as conservators of public morals, in their Blue and Silver Series, so a girl unmarried and without a chaperon would never do for this book.  If they were to publish it in their Yellow Prism Series I could fling all such considerations to the winds, for there they cater to stronger palates, palates cultivated by French literary cooks, and morals need not be considered, provided the story is well told and likely to sell; but this is for the other series, and a chaperon is a sine qua non