As a crucial works of JIkang research, "The Letter to SHAN Ju-yuan in Breaking Off Relations" has permanently caused debate and controversy , most scholars maintained that it had written in Jing Yuan II , i.
其写作时间学界多持魏景元二年,即公元2 6 1年。
According to the conception brought forward by Crocker and Borton(1959),two-year seed is usually the seed with no seedling emergence before second spring coming after its matutity in nursery under natural condition\.
Borton(1959)提出的概念,凡是在苗圃条件下,犹如在自然条件下成熟后的第2个春季来临之前不出苗的种子,通称为二年种子(two years seed)[9]。