First thing I do is try and determine size of the plant. Is it making juvenile pitchers, lower, or something else.
These plants appear large enough to determine they are not making juvenile pitchers. But I feel it is not making full sized adult pitchers either. Probably because of the less than ideal care it received at the store.
Specific characteristics of N. alata.
Leaves usually come off the stem in an upward angle. Mid point of the leaf fairly broad and tapering to a sharp point. There is a clear petiole. Pitchers are bulbous at the base with a slight constriction above that and expanding slightly around the peristome. The peristome has no folded points and is at a noticeable angle from front to back. The lid is large enough to cover the pitcher opening. There is a very distinct internode.
N. ventricosa
Leaves usually are flat off the stem. The leaf blade projects all the way from the stem (no petiole visible) and the leaf is only slightly wider at the tip. Pitchers are bulbous at the base with a constriction and then broadening noticeably around the peristome. The peristome has folded points in it and is nearly horizontal. The lid is not large enough to cover the pitcher opening. Internodes are very short.
What do I see in this picture?
IE why do I think it is not N. ventricosa
Noticeable internodes longer than N. ventricosa. Leaves coming off the stem at a slight angle and noticeably broader in the middle than than the base, with a narrowing at the tip to a sharp point. Large lid that fits the pitcher opening. Peristome at a noticable angle front to back. Pitcher not expanding much above the constriction.
Why do I think it is not N. alata
Leaf margin extends all the way to the stem. Internodes fairly short. Angle of the peristome is not oblique enough.
Why do I think it is N. x Ventrata
Leaf margin extends from the stem outward but the middle of the leaf is much broader with the outer portion narrowing to a sharp point. Internodes noticeable and larger than N. ventricosa but not nearly that of N. alata. Leaves projecting from the stem at a slight angle upward. Peristome at an angle more than N. ventricosa but less than N. alata.
Below is a picture of a typical N. alata (You can barely see the tip of the leaf to the top and left of the pitcher and to the top and right the petiole and stem from a basal shoot)
Picture of a red N. ventricosa on the young side still. (I chose this one since the plant in question is not fully mature either)
Photo of a mature N. xVentrata
For years and years N. xVentrata has been improperly labelled and sold. The subsequent confusion is not surprising. Sometimes the differences are subtle. The N. xVentrata you see in the picture, I received only a couple years ago from another commercial grower. I had ordered a red N. alata.
Tony