In the first sentence, the italicized relative clause serves simply to describe the Italian, not to identify him. The flower is a mere detail of the picture.
In the second sentence, the relative clause serves not merely to describe the Italian, but also to distinguish him from all others. The flower is mentioned as a means of identification. The relative clause confines or restricts the meaning of the antecedent (Italian).
154. A relative pronoun that serves merely to introduce a descriptive fact is called a descriptive relative.
A relative pronoun that introduces a clause confining or limiting the application of the antecedent is called a restrictive relative.
Thus in the first example in [§ 153], who is a descriptive relative; in the second, it is a restrictive relative.
155. Before a descriptive relative we regularly make a pause in speaking, but never before a restrictive relative. Hence the rule:—
A descriptive relative is preceded by a comma; a restrictive relative is not.
- Three sailors, who were loitering on the pier, sprang to the rescue.
- A clumsy weapon, which I took for a blunderbuss, hung over the fireplace.
- I told the news to the first man that (or whom) I met.
- The coins that (or which) you showed me are doubloons.
- Nothing that I have ever read has moved me more profoundly than the third act of “King Lear.”
156. Who, which, and that are all used as restrictive relatives; but some writers prefer that to which, especially in the nominative case.
Note. That is not now employed as a descriptive relative, though it was common in this use not very long ago. Thus in 1844 Disraeli wrote: “The deer, that abounded, lived here in a world as savage as themselves” (Coningsby, book iii, chapter 5).