238 



PLANT LIFE. 



within this case, by which they are protected until mature, or 

 longer. 



These two methods of seed pioduction form tlie basis for 

 the separation of the seed-bearing plants into two great groups, 

 one known as gymnosperms, or plants with nal-;ed seeds, the 

 other as the angiosperms, or plants with encased seeds. 

 Open carpels are found exclusively among the gymnosperms, 

 to which belong the cone-bearing, mostly evergreen, trees, 

 while the closed pistils are chiefly found among angiosperms, 

 to which belong the majority of garden and field plants and 

 the deciduous forest trees. 



334. The simplest form of carpel occurs in Cycas (fig. 

 245), in which the ovules are borne on the edges near the 

 bases of leaves which somewhat resemljle the foliage leaves, 

 and form a whorl between preceding and succeeding whorls 

 of foliage leaves upon the main axis. The carpel of most 



gymnosperms is a scale from 

 whose upper surface arises a 

 similar fleshy scale, the pla- 

 centa, bearing t\\'o o\ules 

 upon its ventral (u])pcr or in- 



FiG. 245. 

 Fig, 245, — An ovule-bearing leaf or carpel nf Cvfas ?vr 



base, replacing tbe branches. On the right abo\'e, a yo 



naturalsize,— After Sachs, 

 Fig. 246, — A young cone-scale (placenta) nf ,Stokh ['ine 



latter halved parallel to the scale, showing the innlyol ( 



ument forming the micropyle, ///, 'rhe scale is attac 



diam, — After Kemer, 



lies near 

 qiurter 



;l'.I integ- 

 abuut S 



