Bebb’s sedge is distributed throughout wetland areas of temperate and subarctic North America. Like most members of the Cyperaceae, or sedge family, it has a wind-pollination strategy (i.e., it is anemophilous), with (relatively) “large anthers, long filaments and prominent stigmas” (source: Wendy Zomlefer’s Guide to Flowering Plant Families). Without the need to attract insects, the flowers are also apetalous and asepalous (lacking petals or sepals). An alternative way of describing this phenomenon is to say that the perianth is absent.
Most identification keys for Carex species require the plant to have mature fruit, one of the many reasons that botanical field surveys of areas without the luxury of being able to continue fieldwork into the late summer or autumn simply state “Carex spp.” (meaning multiple unidentified species of Carex) in the final list of plant species collected. Plants collected earlier in the year with only vegetative and flowering characters can be extremely difficult to identify to species. The plant in today’s photograph likely has mature fruit (or close to it), though the achenes (dry, one-seeded fruits) are hidden within the sac-like perigynia.
Much to the frustration of students learning about the Cyperaceae, though, Carex identification is often difficult even when a specimen has mature fruit. Writers of identification keys sometimes like to throw in a couplet or two about the flowering characteristics midway into the key, which, of course, will not be present in the specimen in front of you (because you collected the plant when it had mature fruit like you were supposed to!). You then learn that a) you actually need to have specimens from the same group of plants in different reproductive stages or b) you need to become a good guesser and expert at the trial and error method of identification. Option b, I think, is quite a popular option.