Fig. 168. — Dioon ediile: semi-diagrammatic reconstruction of vascular system of 

 embryo, showing girdling: col, cotyledon; tb, tubular part of cotyledon; cs, cotyledon- 

 ary strands; l\ to l\, four strands of first leaf; l\ to /*, strands of second leaf; vp, vas- 

 cular plate; a, xylem from protoxylem of the plate to form protoxylem of primary root. 

 — After Thiessen.^''' 



