Fungus without mycelium is

The correct option is Saccharomyces.

Step-by-Step Explanation:

1. Understanding Mycelium:
In the kingdom Fungi, the vegetative body of most multicellular fungi consists of a network of thread-like, branching structures called hyphae. This network or collection of hyphae is collectively known as a mycelium.

2. Analyzing the Options:
- Agaricus: Commonly known as the mushroom, this is a multicellular fungus belonging to the class Basidiomycetes. It has a well-developed, branched septate mycelium.
- Puccinia: A rust fungus (Basidiomycete) that is a parasite on plants. It possesses a highly developed mycelium that grows inside the host tissues.
- Albugo: An obligate plant parasite (Oomycete/fungus-like organism often studied under fungi) that also develops a intercellular mycelium with haustoria to absorb nutrients.
- Saccharomyces: Commonly known as yeast, Saccharomyces is a unicellular fungus belonging to the class Ascomycetes. Since it is unicellular, it exists as single cells and does not form a true filamentous vegetative body or mycelium. Under certain conditions, budding cells may remain attached to one another, forming a temporary chain called a pseudomycelium, but a true mycelium is entirely absent.

3. Conclusion:
Therefore, the fungus that exists without a mycelium is Saccharomyces (yeast).