APPENDIX 



517 



ch 



B 



FIG. 4. Head of yarrow 



A, top view (magnified); B, lengthwise section (magnified), re, receptacle; i, 



involucre; r, ray flowers; d, disk flowers; c, corolla; s, stigma; ch, chaff or 



bracts of receptacle 



A B 



FIG. 5. A, panicle of oat ; B, compound umbel of carrot 



