His reverence for nature and especially for trees, combined with his affinity for the female nude, resulted in his most distinctive and widely exhibited paintings, depicting dryads in the woods.

[2][3] His circle of friends included the artists Édouard Debat-Ponsan, Edmond Debon [fr], Adrien Demont, Virginie Demont-Breton, Octave Jahyer [fr], Henri Pille, Tony Robert-Fleury, and François Thévenot;[4] the painter Edmond Yon [fr], in whose garden at Rue Lepic, n° 59, Guay painted nature studies;[5] and the author Léon Roger-Milès, who dedicated to Guay his story "Une Vision d'Allori", which imagines a dream of the Florentine painter Cristofano Allori as a starting point for a rapturous meditation on the transcendent beauty of the female nude.

[6] The popular singer-comedian Ernest Gibert (who was to die in a spectacular accident a few weeks later)[7] entertained at an 1892 New Year's Eve party chez Guay.

In 1873, at the age of 24, he had a painting accepted for exhibition at the annual Paris Salon, the traditional starting point for the career of a French artist of the 19th century; the work was Ulysse suspendu sur le gouffre de Charybde, inspired by a passage in Homer's Odyssey.

By 1877 some of his paintings had made their way to San Francisco, where the art dealers Snow and May sold two of his works at auction, The Anglers and A Fishing Party.

[10][11] Another work by Guay created a sensation in San Francisco at the 15th Mechanics' Fair of 1880.The Awakening showed a nude woman, life-size, lying on her side and just waking up.

She was too contemporary, a modern-day woman, "the very embodiment of flesh, blood, and passion," portrayed after what some said was surely a night of debauchery.…Alarmed, the fair managers hung an unsightly red drapery over the offending nude as they tried to decide what to do next.…Gallery visitors, young and old, took to peeping behind the drapery [which] kept falling down, so a policeman was posted next to the painting to ensure public safety until…a vote would be taken among gallery visitors to determine whether The Awakening should stay or go.

"Speaking in a general way," wrote the Chronicle the next day, "all the good-natured, sleek and healthy people appeared to be in favor of allowing the picture to remain and all the dyspeptic and melancholy ones determined to have it removed.

His genre painting En l'absence du maître (While the Master's Away) of 1877 is also known only from reproductions, including a full-page engraving published in L'illustration: journal universel.

At least one of his paintings is known to have been destroyed in the carnage of World War II: La mort de Jézabel, exhibited at the Salon of 1888, where it inspired the critic Henry Houssaye to write a vivid description:On the hard slabs, at the foot of a massive square tower covered at its base with blue tiles, lies with its head in front and arms outstretched the corpse of the Queen of Israel.

Despite the murder that has just been committed and despite the carnage about to occur, we are less moved by the drama than we are struck by the power of the execution and seduced by the charm of the coloring.

While Guay's submissions to the Salon followed the rigorous standards of Academic art, and were sometimes quite large, he also painted a series of smaller works depicting rustic villages and farm houses in locations including Brittany and the Vosges region of France.

Often executed in oil on panel, presumably painted en plein air, these display a looser, almost impressionistic brushwork, and may have been made as studies, souvenirs, and gifts.

[7][8] It was in his paintings of forests and dryads that Guay most distinctly expressed his artistic vision and most successfully struck a chord with popular taste and critical reception; "his talent was transformed in the attentive study of nature.

La mort du chêne (The Death of the Oak) followed in 1891, inspired by a poem by Victor de Laprade: "When the man struck you with his cowardly ax,/O king whom the mountain yesterday carried with pride,/My soul, at the first blow, resounded with indignation,/And in the holy forest there was great mourning…"[17][18] The location of the painting is unknown.

The painting was inspired by a poem by Émile Blémont [fr]: "A mournful silence filled the great woods,/Once peopled with such sweet visions./Pan had just expired.

Look closely, and you will discover silhouettes of nymphs and fauns; they are the forest divinities for whom the poet Ronsard wept, being carried away in this cloud of smoke.

The undated work La Couture presents a domesticated dryad; a very real woman, not naked but entirely clothed, is perched on the stump of a tree not unlike a pedestal, content to sew.

After Gerôme's death in 1904, Guay carried forward the principles of Academic art into the 20th century, even as it faded from fashion, a once mighty forest felled by Impressionism.