A lot in a little, but withal, transparent

There are those people who (surely without too much justification) have surrounded the fritillary with an air of sadness. Perhaps they have overreacted to the shadowy maroon of its flowers - which can also be a happy cream-white - or to its hung head. Admittedly these small lanterns do not suggest a carnival exuberance as much as a secretive and reticent fragility; but such gloomy local tags as ''Doleful Bells of Sorrow'' or ''Drooping Tulip'' hardly seem fair to its peculiar beauty. And to call it ''Widow Wail,'' as they do in Shropshire, is a positive insult to its light graces.

However, as Geoffrey Grigson has pointed out in The Englishman's Flora, the Elizabethans, who could be heartily morbid when they chose, found fritillaries to be only ''pleasant'' and ''beautiful.'' They planted them in their gardens and wore them on their bosoms. They were charmed above all by the patterning on the petals to which both of the plant's Latin names - ''Fritillaria'' and ''meleagris'' - allude. The first, according to Gerard (although it literally means ''dice-box''), seems to refer to ''the boord upon which men plaie at chesse, which square checkers the flower doth very much resemble.'' The second name means ''guinea fowl,'' and points to a similarity between this eccentric domesticated bird's speckled feathers and the fritillary's petal markings.

I had to wait, this spring, to see our fritillaries come into flower to convince myself that this delightful tessellation really is the geometry of nature and not the simplification of art: but the delicate bells certainly were covered with minutely precise rectangular mosaics, just as Charles Rennie Mackintosh depicts them.

The best name of all for this flower is surely ''snake's head,'' because it describes the shape and inclination of the flowers (just before they open fully) and also their ''scaly look,'' as the poet Hopkins phrases it. The plant as a whole has also, in its disposition, something of the enigmatic quality of a snake. It belongs, in a way, to the decorative and fanciful world of ''art nouveau.'' The exquisitely controlled sinuosity of the tall green stem as it supports the head must have had an instant attraction for an artist-architect of Mackintosh's turn-of-the-century sensibility.

This imaginative Scottish designer of buildings and furniture has tempted more than one historian to call him a ''genius.'' The inventiveness of his work, an amazing mixture of restraint and excitement, of downright practicality and decorative invention, looks in two directions with a sense of vision which doesn't allow for conflict. It looks towards the ornate vegetation of ''art nouveau,'' and it looks towards the severe rectangularities of Modernism. It is simultaneously sensuous and puritanical, organic and geometrical.

If there is a perfect flower for Mackintosh to have painted, it must be the snakeshead fritillary. With his architectural practice run down, and having left his native Glasgow, where his outspoken modernity and originality were none too popular, his affection for flowers prompted him to work on a book of flower paintings. Though World War I apparently made its publication out of the question, many of his studies of wild and garden plants survive. They are elegant, assured and scrupulous. They have the detail of botanical drawings, the economical flattened design of old herbal woodcuts and the nicety of fine architectural draughtsmanship. With a hint of Cubism, he shows the outlines of leaves and petals as uninterrupted: crossing over but not effacing each other. In this way he suggests their transparency, and the traceable completeness of their structure.

I would love to know what Mackintosh thought when he first saw a fritillary. The slender verticality of its stems, the flexuous interlace and arabesque of its leaves - the way they touch and separate - and of course the minute checkerboard of the petals: all are pure ''Mackintosh.'' His architecture had been for years displaying his delight in just these things. Did he come across the unpretentious meadowflower only in 1915 and see then for the first time how exactly it was his flower? Or had he studied it carefully years earlier and consciously based his architectural details, his stylized curves and verticalities, his accumulations of squares, little and big, on this modest work of nature? I prefer the first theory.

If I am right, the encounter in 1915 at Walberswick in Suffolk (where the drawing was made) between architect and flower must have been a sudden, quiet recognition of similar aims. Mackintosh must have found in this wonderful flower the same natural qualities he had achieved by ''art.'' Both knew the mystique and significance of restraint, both knew the aesthetic finesse of slender elongation, both knew the energy and charm of checks and squares. Both could be praised - as a contemporary of Mackintosh's praised his thin shafts of white wood embellishing a bedend or supporting a lean mantelpiece, his decorative ironwork, or his tall, fantastic standard lamps - for their ''lines of a shy elegance.''