Explanation

Linkage was first demonstrated in plants by William Bateson and Reginald Punnett using sweet peas (Pisum sativum), but the classic demonstration of linkage groups and crossing over in plants is often attributed to Thomas Hunt Morgan's work on Drosophila. However, for plants specifically, the first attempts are usually associated with Bateson and Punnett's work on sweet peas or later work by others. Wait, let me double-check. Actually, the first demonstration of linkage was in sweet peas (Pisum sativum) by Bateson and Punnett. But option C is 'Possum sativa' which is a typo for Pisum sativum. Option D is 'Zeal Mays' which is likely Zea mays (corn), used by Emerson and East or others later. Let's re-evaluate. The question asks for the first attempt to show linkage in plants. Bateson and Punnett discovered linkage in sweet peas (Pisum sativum) in 1905. Option C says 'Possum sativa', which is clearly a typo for Pisum sativum. Sweet peas are Lathyrus odoratus, not Pisum. Wait, sweet peas are Lathyrus odoratus. Peas are Pisum sativum. Bateson and Punnett worked on sweet peas (Lathyrus odoratus). So option A 'Lathers odorous' is a typo for Lathyrus odoratus. This matches the historical fact. Therefore, A is correct despite the typos.