I claim the ornamental design for a fluorescent lamp, as shown and described.
FIG. 1 is a top view of a fluorescent lamp of the present invention;
FIG. 2 is a front view thereof;
FIG. 3 is a first side view thereof; and,
FIG. 4 is a second side view thereof.
The middle portion of the fluorescent lamp is omitted in FIGS. 1 and 2 for convenience of illustration, but the cross-section thereof is understood to be identical along the length.