Which of the following is not a Basidiomycetes ?

Options

A. Agaricus
B. Ustilago
C. Aspergillus
D. Puccinia

Answer

To determine which of the following is not a Basidiomycetes, we will analyze each option provided:

1. **Agaricus**: This is commonly known as the mushroom. Agaricus belongs to the Basidiomycetes class of fungi. Therefore, it is a Basidiomycete.

2. **Asteligo**: This refers to smut fungi, which are also classified under Basidiomycetes. Thus, Asteligo is a Basidiomycete.

3. **Paxinia**: This is known as rust fungi, which are included in the Basidiomycetes as well. Hence, Paxinia is a Basidiomycete.

4. **Aspergillus**: This is a genus of fungi that is classified under Ascomycetes, commonly referred to as sac fungi. Therefore, Aspergillus is not a Basidiomycete.

Based on the analysis, the organism that is not a Basidiomycete is **Aspergillus**.

### Step-by-Step Solution:
1. Identify the classification of each option.
2. Determine if each option belongs to Basidiomycetes.
3. Conclude which option does not belong to Basidiomycetes.

### Final Answer:
The correct option that is not a Basidiomycetes is **Aspergillus**.