MICROSCOPIC STRUCTURE OF WEED SEEDS 



561 



UMBELLIFERAE, PARSLEY FAMILY. 



Sweet Cicely (Osmorrhiza longistylis (Torr.) D. C). 



The epidermal cells are longer than broad, the outer walls are 

 thickened, five to six rows of thin-walled parenchyma cells occur 

 underneath the epidermal layer; the ribs contain the vascular ele- 

 ments, thick-walled sclerenchyma cells; the testa consists of a 

 layer of thin-walled parenchyma cells, p, followed by a layer tan- 

 gentially elongated and another of large parenchyma cells, p 1 , and 

 the compressed nucellus, n. 1 The endosperm consists of large thin- 

 walled cells. 



Fig. 42 8. Microscopic structure of some Umbelliferous weeds. 

 I. Sweet Cicely (Osmorhiza lonyistylis) . II. Cow Parsnip (Heracleum lana- 

 tum). III. Wild Carrot (Daucus carota). Underneath, parenchyma cells, 

 thick-walled sclerotic parenchyma, sectional view to the right. 

 n=nucellus. p=parenchyma. t=testa. en=endosperm. ep=epidermis. o=oil 

 duct. 



(Drawings by L. H. Pammel.) 

 36 



