**Asexual Modes in Bryophytes**

Bryophytes are a group of non-vascular plants that includes mosses, liverworts, and hornworts. These plants reproduce through both sexual and asexual modes. Asexual reproduction in bryophytes involves the production of new individuals without the involvement of gametes or fertilization.

Among the given options, **option B (Gemmae)** is not an asexual mode in bryophytes. Let's understand why:

**1. Budding:**
Budding is a common asexual mode of reproduction in bryophytes, particularly in liverworts. In this process, a new individual develops as an outgrowth or bud from the parent plant. This bud eventually detaches from the parent and grows into a new independent organism.

**2. Fragmentation:**
Fragmentation is another asexual mode of reproduction observed in bryophytes. It involves the breaking of the parent plant into smaller fragments, each of which can grow into a new individual. This process is commonly seen in mosses, where portions of the moss plant break off and develop into new plants.

**3. Sporophyte Formation:**
Sporophyte formation is a crucial phase in the life cycle of bryophytes. It involves the development of a sporophyte, which is the diploid phase, from the gametophyte, which is the haploid phase. The sporophyte produces spores through meiosis, which eventually germinate and give rise to new gametophytes. Although sporophyte formation is not an asexual mode of reproduction, it is an essential part of the bryophyte life cycle.

**4. Gemmae:**
Gemmae are small, multicellular structures that can be found in some liverworts, such as Marchantia. These gemmae are produced in specialized structures called gemma cups or gemmae cups. Gemmae are not involved in asexual reproduction but rather in vegetative propagation. They are small, lens-shaped structures that contain a group of cells capable of growing into a new liverwort plant. When the gemmae are dispersed from the gemma cups, they can germinate and develop into new individuals.

Therefore, among the given options, gemmae (option B) is not an asexual mode of reproduction in bryophytes. The correct answer is option B.