LONDON — A glass tulip perched a thousand feet above London may be the next striking addition to the British capital’s ever-changing skyline, according to plans announced by the architect Norman Foster’s studio on Monday.

When a bullet-shaped skyscraper, a creation of the Foster studio that quickly became known as the Gherkin, opened in 2004, its curved lines made it a curiosity in the city’s skyline. The building, officially 30 St Mary Axe, was a bold addition to London’s historic financial center, known as the City.

Since then, the race to stand out on the London horizon has sped up, with unusually shaped towers known — officially or not — as the Shard, the Cheese Grater and the Walkie Talkie. At the same time, the Gherkin became less visible, almost enclosed in a thicket of other skyscrapers that is only going to grow in coming years.

The proposed new tower, the Tulip, would raise the aesthetic stakes, with a glass structure like a closed tulip blossom, echoing the shape of the Gherkin, on an elongated concrete stem, high above its neighbors.