538 



BOTANY OF CROP PLANTS 



primary ribs are thread-like, while the lateral ribs are expanded 

 into broad, flat wings, with those of the two mericarps con- 

 tiguous. The oil tubes are solitary in the intervals; there 

 are four on the dorsal side and two to four on the commissural 

 side. The olive-green seeds are flattened dorsally. The 

 seeds are very short-lived. 



Geographical.' — The wild parsnip, Pastinaca saliva, from which our culti- 

 vated varieties are derived, is a native of Europe. This wild form has be- 

 come naturalized in many sections of North America, bccurring as a weed 

 along roadsides and in waste places. 



Varieties. — There are comparatively few parsnip varieties. 

 Probably the most popular sorts are the Guernsey and Hollow 

 Crown. In both of these, the crown is concave. 



Fig. 



-Celery (Apium graveolens). A, schizocarp, external, X 15; B, 

 diagrammatic cross-section of schizocarp, X 20. 



APIUM (Celery and Parsley) 



Generic Description.— Members of this genus are annual 

 or perennial herbs with pinnately divided leaves. The white 

 or greenish flowers are in compound umbels. The involucre 

 and involucels may be present or wanting. The calyx teeth 



