MODERN design in flower arranging does not rely on a large quantity of material for effect but on the imaginative use of a little, according to Marian Aaronson, internationally known British designer, lecturer, judge and demonstrator of the art of floral design.

Aaronson is the author of a new book, "Flowers in the Modern Manner," (published by Grower Books, London, England; distributed in the United States by International Scholarly Book Services, P.O. Box 1632, Beaverton, Ore. 97075; 160 printed pages, beautifully illustrated, $19.95). In the book she arranges beautiful and slightly ethereal designs, and then explains with the aid of artist's drawings just how the idea was arrived at and carried through.

"When in doubt or striving for improvement," she writes, "it is helpful to ask the following questions:

"Is the selection of material and everything used suitable and harmonious to the nature and purpose of the design envisaged?

"Is anything superfluous? Be ruthless, query the function of each unit and its design contribution.

"What is missing? Not enough contrast? Can presentation be improved by raising the arrangement, or altering the angle at which it is viewed? Would background help?

"Does the finished composition appear unified? Are the proportions and the balance pleasing? Does any area dominate at the expense of the overall interest of the design?"

Q. I had potted geraniums on my ratio and they bloomed almost all summer. I brought them indoors in November, put them in a sunny window, and they haven't bloomed since. Is there anything I can do about it?

A. During December and January, when days are short, and especially if there are cloudy days, the geraniums rarely get enough sunlight to bloom. They will grow and bloom with only five or six hours of sunlight daily but it must be almost every day. When the days are longer in late February and March, they should bloom nicely for you. Indoors, these plants like cool temperatures at night, 50 to 60 degrees Fahrenheit, and they should be allowed to dry out before being watered again.

Q. I have acorns from a beautiful oak tree in my refrigerator; I picked them up off the ground under the tree. When is the best time to plant them?

A. Acorns of most species of white oak should be planted immediately after being collected. Those of black oak can be planted immediately or stratified (stored in moist, well-drained sand or sand and peat, for 30 to 90 days, at 32 to 41 degrees Fahrenheit). There is a strong probability insects may have ruined the acorns you have while they were on the ground. Once damaged, they will never germinate.