To solve this problem, we need to understand the process of spore formation in fungi.$\newline$Karyogamy followed by meiosis is a process that occurs in the life cycle of fungi, leading to the formation of spores.$\newline$In fungi, spores can be produced either endogenously (inside a structure) or exogenously (outside a structure).$\newline$Let's analyze the options:$\newline$• Option 1: Agaricus$\newline$ - Agaricus is a genus of basidiomycete fungi, which includes the common mushroom.$\newline$ - In Agaricus, spores are produced exogenously on basidia, which are specialized spore-producing structures.$\newline$ - After karyogamy and meiosis, basidiospores are formed on the outside of the basidium.$\newline$• Option 2: Alternaria$\newline$ - Alternaria is a genus of ascomycete fungi.$\newline$ - In Alternaria, spores are produced endogenously within asci, not exogenously.$\newline$• Option 3: Neurospora$\newline$ - Neurospora is also an ascomycete fungus.$\newline$ - Spores are produced endogenously within asci.$\newline$• Option 4: Saccharomyces$\newline$ - Saccharomyces is a genus of ascomycete fungi, including yeast.$\newline$ - Spores are produced endogenously within asci.$\newline$Therefore, the correct option is Option 1: Agaricus, where spores are produced exogenously.