Very perceptive question. In earlier times all men wore suits. The lapels had buttonholes but no buttons. They were just vestiges of earlier coats. Many men would wear a single flower in one of the buttonholes. There are probably very few men who do this anymore, although many men wear little pins of one kind or another, including American flags. The buttonholes on most suit coats and sport coats may not even be made to be opened but are sewn tight shut. Buying a flower from a street vendor was an small extravagance. Men did it mainly to show that they could afford a little luxury. It was also, I assume, an act of charity for the poor women who sold flowers on the street. Most of these flowers must have been bought by men. Apparently the standard price for a single small buttonhole flower at that time was ninepence. In those days there were twenty shillings in a pound and 12 pence in a shilling. That meant that there would be 240 pennies in a pound. The pennies were made of copper and were about the size of an American half-dollar.
Eliza Doolittle in George Bernard Shaw's play Pygmalion (1913), which was made into a musical titled My Fair Lady, was a flower girl selling flowers on the street in London. That was how she met Henry Higgins, a phonetics professor, who taught her to speak like a lady and then fell in love with her. Charlie Chaplin as the "Little Tramp" buys a buttonhole from a blind flower girl as an act of charity in his classic film City Lights (1931).
The French word for "buttonhole" is "boutonniere." According to Wikipedia:
A boutonnière (French: [butɔnjɛʁ]) is a floral decoration worn by men, typically a single flower or bud. Boutonnière is the French word for “buttonhole”.
The delightful short story "Dusk" told in Saki's typical style of irony and surprise, brings to mind two important points: the hubris of the wealthy at that period of England's history, and the difference between reality and appearance.
The story's title comes from the time of day when our main character, Gortsby, is sitting on a bench near the section of London called Hyde Park Corner. During the daytime hours, it was a highly traveled area; and the park was a place where the well-to-do would stroll or ride, often to be seen by members of the haut ton, the society's elite. However, Gortsby observes, at dusk it is a totally different world:
The scene pleased Gortsby and harmonised with his present mood. Dusk, to his mind, was the hour of the defeated. Men and women, who had fought and lost, who hid their fallen fortunes and dead hopes as far as possible from the scrutiny of the curious, came forth in this hour of gloaming, when their shabby clothes and bowed shoulders and unhappy eyes might pass unnoticed, or, at any rate, unrecognised.
To Gortsby's mind, only those who were "defeated" in some way came out at dusk. It is ironic after a fashion that he, too, is out at dusk—though he does not fully categorize himself as one of these unfortunate souls. (He discloses that he has no financial problems, but makes a vague reference about those defeated like him—those with a shared misfortune. Perhaps he finds himself socially unacceptable.) But even so, he shows no mercy, but criticizes others with a heavy hand:
He had failed in a more subtle ambition, and for the moment he was heartsore and disillusioned, and not disinclined to take a certain cynical pleasure in observing and labelling his fellow wanderers as they went their ways in the dark stretches between the lamp-lights.
Quick to generalize about those roaming about as losers, Gortsby (who prides himself in knowing so much, especially about the those beneath him) forgets that with the falling of the sun, there are also undesirables (thieves) moving through the area as well.
Gortsby's arrogance is apparent in his statement as to who had the right to be in this area by day, which is implied with his statement that the disadvantaged were out of place:
...they came out in this bat-fashion, taking their pleasure sadly in a pleasure-ground that had emptied of its rightful occupants.
The near-darkness symbolizes a lack of knowledge. While lights shining from nearby windows almost dissolve the cloak of darkness covering those passing by, it is not enough to fully expose the people or, in this case, shine a beam of enlightenment. Gortsby is obviously a man of some reasonable intelligence, but his stereotypical perceptions prevent him from seeing what is about to happen to him, in the dusk.
Gortsby is quick to study and judge the old man sharing the bench with him.
His clothes could scarcely be called shabby, at least they passed muster in the half-light, but one's imagination could not have pictured the wearer embarking on the purchase of a half-crown box of chocolates or laying out ninepence on a carnation buttonhole.
While his neighbor is not shabbily dressed, Gortsby makes assumptions about the man's meaningless existence. That while he has an air of defiance about him (perhaps he is not ready to be dismissed by those younger than himself), Gortsby notes that he probably was no longer able to defy anyone or anything. And the old man's ability to pay his bills, Gortsby sneeringly notes, is the only thing of interest about him. Callous and dismissive, Gortsby studies the next occupant of the bench when the old man leaves. This new man commands Gortsby's attention simply by his appearance:
...his place on the bench was taken almost immediately by a young man, fairly well dressed but scarcely more cheerful of mien than his predecessor.
Gortsby's judges his new neighbor by his youth and quality of dress. The young man is seemingly in the throes of some calamity and so Gortsby's asks what the problem is:
The young man turned to him with a look of disarming frankness which put him instantly on his guard.
The young man turns a "disarming" and "frank" countenance upon Gortsby. Perhaps because our protagonist is cynical, he is instantly on his guard. If Gortsby had had the presence of mind to recall that unsavory types are about all the time, but especially during dusk and darkness, he might have paid closer attention. However, he is so taken with his (ostensible) brilliance of thought, he lets his guard down. Hearing the young man's tale of being lost and unable to find his hotel, Gortsby recalls being in a similar situation. However, his empathy for the young man disappears for two reasons. First, Gortsby was smart enough to find his way back to his hotel. Second, the soap the young man left his lodgings to buy is nowhere on his person. Gortsby disdainfully dismisses the young man for trying to cheat Gortsby out of a loan without paying careful enough attention to the details of the younger man's ruse.
"To lose an hotel and a cake of soap on one afternoon suggests wilful carelessness," said Gortsby...
The young man quickly leaves. Gortsby is very full of himself, extremely proud that he outfoxed the fox that was after his cash.
Suddenly, however, Gortsby looks down and sees a neatly wrapped package of soap. Believing the younger man's story, he rushes off to find him:
You must excuse my disbelief, but appearances were really rather against you, and now, as I appealed to the testimony of the soap I think I ought to abide by its verdict. If the loan of a sovereign is any good to you —
For all of his aptitude, Gortsby makes a judgment call based upon appearances. He still has no way of knowing if the young man really was ever checked into a hotel. He has just told himself—and the young man—that the importance of the story was in the details. Having the soap to begin with would have been wise on the part of a thief who had not enough to buy lodging for the night, but could afford a bar of soap.
As Gortsby returns to the bench, he finds the old man who he had summarily dismissed earlier as a person of little consequence, unworthy of his attention, looking for something he has lost—his bar of soap!
Because the man was older, Gortsby decided he was not worth noticing; and he ended up being fleeced by the thief he had almost escaped. It is ironic that the old man was all he appeared to be—a man of some substance; and the well-dressed young man was a liar and a thief. Gortsby's prejudices blinded him to the truth.
Gortsby could not imagine the old man capable of buying chocolates or a flower for his buttonhole, making these the guidelines by which he judged the old man's value. Then, while Gortsby first believed that the young, well-dressed man was capable of spinning a tale that was hard to accept, later he accepted his story because the young man was well dressed and because of the soap, not because he was the better man. Appearances convinced Gortsby—not reality.