What they made on their summer vacations

“Call of the Coast’’ is a collaboration between the Portland Museum and the Florence Griswold Museum in Old Lyme, Conn.; all the works are drawn from these two collections. So this show is exclusively about the art colonies of Maine and Connecticut. Provincetown and Gloucester, both wildly fertile spots for painting in their time, are conspicuously missing.

The decision to exclude these giants seems to be an economic one. Bringing in Gloucester and Provincetown would have meant partnering with two more institutions, shipping more canvases, and been costlier. And it would have clouded the intriguing point “Call of the Coast’’ elucidates: Artists at the Connecticut colonies were more conservative; the Maine painters were more daring. These art colonies came to prominence around the turn of the 20th century, on the cusp of modernism.

Portland curators Thomas Denenberg and Susan Danly, and Griswold curator Amy Kurtz Lansing, have put together a lean exhibit that spotlights dramatic differences between the Connecticut colonies of Cos Cob and Old Lyme and the Maine hot spots, Ogunquit and Monhegan Island. The show also considers how painters romanticized New England rural life, and contributed to the branding of New England as quintessentially American.

Art colonies sprang up in the latter years of the 19th century, in part because labor and commerce, which had buzzed up and down the coast, went inland with industrialization, and shorelines began to draw more and more vacationers. American artists followed the lead of their French mentors, who had defected from Paris for Giverny or Barbizon to paint outdoors.

The Americans were drawn in by the native culture. Yankee fishermen and local architecture represented to these artists a life simpler and closer to the heart than they found in the big city bustle of New York and Boston.

“Call of the Coast’’ is organized colony by colony. Many artists, such as Frederick Childe Hassam, flitted from one to the next; still, each had its particular characteristics. The colony at Cos Cob has the earliest origins of the four, in the 1870s, but it coalesced around painters Robert W. Weir and John Henry Twachtman. Both taught there in the 1890s; both were Impressionists.

Among their students was Ernest Lawson, whose “Connecticut Landscape’’ (circa 1902-04) is a shimmer of quick, crosscutting brushstrokes; it’s hard to distinguish the dappled sunlight on the brook he paints from the flashes of reflection on the grass at its edge. American Impressionist painting is generally more mannered, and certainly less groundbreaking, than the work of its French progenitors. Still, it was the hot commodity at the time, and the Cos Cob crowd was an experimental group.

Although both Cos Cob and Old Lyme are situated near Long Island Sound, the Connecticut painters were not drawn to the sea, preferring to paint inland scenes and quaint local churches and homes. The placid, luminist seascapes popularized by such artists as Fitz Henry Lane (up in Gloucester!) in mid 19th century had fallen out of favor; marine paintings were passé.

Old Lyme crystallized as a colony in 1900, when artists began to flock to Florence Griswold’s boarding house. An early leader there was Henry Ward Ranger, whose soft touch and warm palette characterized the tonalist style, a more conservative approach that harkened back to Lane. You could tumble into the cloudy sky in Ranger’s “Long Point Marsh’’ (1910). Hassam stopped through; his antics were evidence of the jocular mood at the Griswold House. One day, Lansing says in her catalog essay, he ambled through town to the Post Office in a dressing gown and a stovepipe hat, shocking the locals.

Hassam prompted a switch in the Old Lyme crowd from tonalism to Impressionism. His brushy, humming “The Ledges, October in Old Lyme, Connecticut’’ (1907) sets the slender verticals of saplings against rugged boulders rising like mammoths behind them in a warm orange wood.

Soon thereafter, Ogunquit became a cultural battlefield, with the Boston Impressionist Charles Herbert Woodbury on one side of Perkins Cove, and the brash New York modernist Hamilton Easter Field on the other. Woodbury started teaching there in 1898; most of his students were well off Boston women. Field set up shop in 1911. Woodbury and his acolytes painted landscapes and genre scenes, such as his own briskly rendered “Ogunquit Bath House With Lady and Dog,’’ circa 1912, with the swoop of his brush across the sand almost enveloping the faceless lady.

The modernists viewed Ogunquit through a different lens. Where the Impressionists saw light, the modernists saw form and pattern; their palette had less sparkle and more sustained passages of pure, bright tones. And, unlike the Impressionists, they took a deep interest in the figure. You can see all these tools coming out of Abraham Walkowitz’s toolbox in “Old Home, Ogunquit, Maine’’ (1926), in which several women loll on the lawn in front of a Y-shaped tree.

The shining jewel of these four art colonies, and the culminating section of “The Call of the Coast,’’ is Monhegan Island, a magnet for forward thinkers such as Robert Henri, Edward Hopper, and Rockwell Kent. Hopper’s “Monhegan Houses, Maine,’’ circa 1916, is one of his slighter works, an early one, but you can see his vision developing in the clean planes of buildings, with an azure sea and green-tufted hills in the background.

Kent’s “Wreck of the D.T. Sheridan’’ (circa 1949) is my favorite piece in the show, with its saturated blue and yellow sky, and the trimly rendered horizontal of a rusted ship’s hull washed ashore among the sea foam and stones. The Monhegan section moves right through the mid 20th century, so it has the force of art history’s evolution behind it, whereas the other sections capture a major moment of transition.

Gloucester, with its reach back to the 1850s, and Provincetown, which dove headfirst into Abstract Expressionism, may have cluttered the picture, but they would have deepened the story.