One of the more adulatory friends of Paul Cezanne in his later years described seeing the artist in virtual communion with an ancient olive tree just outside his studio. Whatever one thinks of the exaggerated terminology - ''He stroked it. He spoke to it. . . . Cezanne the recluse listened to the olive tree. The tree's wisdom entered his heart . . .'' - Cezanne's paintings, and none more so than those after 1900, do witness to the deep significance trees held for him.
We have had a tendency, later in the century, to look at these last paintings unnaturally, as though they were consciously theoretical, or somehow knowingly initiated Cubism and even abstraction. It is true that Cezanne called himself the ''primitive'' of a new style. But Lawrence Gowing, in his highly illuminating essay ''The Logic of Organized Sensations,'' is surely right to redress the balance by saying: ''The styles that Cezanne has inspired are hardly the promised land he foresaw.''
As Gowing points out, Cezanne's art took its essential life from two things: from ''theory'' certainly, which he often propounded in words of scrupulous meaning; and from direct confrontation with nature. Photographs of exact places painted by him indicate his extreme concern for a true representation of the motif in front of him. In this his art differed markedly from subsequent work, however indebted to him it may have been.
If therefore one looks at a magnificent example of his late style such as ''The Big Trees'' (a gift received recently by the National Gallery of Scotland) as above all an abstract tribute to trees in general, and to their typical power and vigor, one would be only half right. These are specific trees. It seems certain that he painted them on the spot. There is a watercolor of the same subject as this oil, but the two versions have different proportions, and the configuration of branches, as well as the intervals between the trunks, vary from one to the other so richly and subtly that each must have been an independent study of the same subject. The oil is by no means worked up from the watercolor.
To make more than one painting of the same subject was characteristic of late Cezanne. His continual painting of ''Mont Sainte-Victoire'' is the more considerable and well-known example. Similarly, in 1906, he wrote that he was finding plentiful subject matter ''on the edge of the river'' and added: ''. . . the same subject seen from a different angle gives a subject for study of the highest interest and so varied that I think I could be occupied for months without changing my place, simply bending a little more to the right or left.''
This intense preoccupation with slight variations in the viewing of something also occurs within single paintings. In ''The Big Trees'' no contour is final and fixed. The dynamics of the picture are in its multiplicity. But at the same time it is as though he looked for a way to balance, or tie down, this excitement, these confusing choices, by means of a pivot conveniently provided: The vertical and slender tree in the middle introduces an orderly, even geometrical, measure - a steadying center for the picture. It is the classical note in an otherwise almost baroque composition. This contrast between the held and the free might be seen as an illustration of Cezanne's attitude to the differences between ''art,'' which is contrived and ordered by man, and ''nature ,'' which is to be externally studied and learned from. He himself defined art as ''a harmony parallel with nature.'' It was a phrase carefully put together.
Certainly this painting takes its very existence from observation of natural phenomena. It concentrates a fiercely experienced admiration for the way trees relate to earth, the way they extend their branches, and the way their foliage envelopes space, making it both solid and airy. But all this is in the undisguised language, the unmistakable imagery, of brush and paint: it is man-made, integrated, centered. It is a contrast of tones, and contrast of forms. It is a monumental statement but very far from static. It attains its own kind of energy, its own dispersal and collection of forces. And it unifies, as only Cezanne could, in his last paintings, the definite and the tentative. Everything in it is positive. Everything is potential.