资料来源 : pyDict

前形成层

资料来源 : Webster's Revised Unabridged Dictionary (1913)

Procambium \Pro*cam"bi*um\, n. [NL. See {Pro-}, and {Cambium}.]
   (Bot.)
   The young tissue of a fibrovascular bundle before its
   component cells have begun to be differentiated. --Sachs.