KUTRITIOX. 



177 



chouc and gutta-pen ha occur in the milky juice of certain 

 plants. 



253. Nitrogenous by-products. — Among the nitrogenous 

 waste materials the most important are the alkaloids, such as 



Fir.. 17.S. — .Section through oil-receptacles in rind of orange. <i. structure at the beginning 

 of the disorganization of the oil-producing cells: /', final condition, \\\x\\ two drops of 

 oil occupying the ca\'ity. Moderately magnified- — After Tschirch. 



Fig. 



179. 



Fig. 179. — A flower of the red currant cut in half. The roughened surface of the cup, n, 



secretes nectar. I\Iagnified 5 diam. — After Kemer. 

 Fig. iSo. — I. a petal from the flower of a buttercup {Raizitjtculus acris), showing the 



nectary, ji. Magnified 3 diam. II, diagi-am of a longitudinal section of the same 



through the nectary n. I'he tissue lining the poucli of the petal, /■, secretes the drop 



of nectar, /. .Magnified .^ diam. — .After liehrens. 



quinine, morphine, str\-chnine, nicotine, etc., which occur in 

 the seeds, bark, or leaves, and arc gotten rid of when these 

 are dropped. 



