198 



OUTLINES OF PLANT LIFE. 



are not in any respect comparable to the real eggs (since they 

 are produced by the non-sexual or sporophyte phase), the 

 name is retained for convenience. The ovules arise usually 

 upon the ventral (inner) face or the edges of the carpels. 

 In the open carpel they are exposed, but in the closed carpels 

 they are completely shut in, except for a narrow opening 

 which sometimes remains, by which the interior cavity com- 

 municates with the outside air. 



281. Gymnosperms and angiosperms. — ^When the changes 

 through which the ovule passes are complete, it becomes the 



seed. When the ovules are produced 

 upon the free surface of an open carpel, 

 the seeds are, therefore, exposed. On 

 the contrary, when the ovules are borne 

 ithin a closed pistil (formed by one or 

 ore carpels) the seeds are developed 

 ithin this case, by which they are pro- 

 cted until mature, or longer. 

 These two methods of seed produc- 

 tion form the basis for the separation 

 of the seed-bearing plants into two 

 great groups, one known as gymno- 

 sperms, or plants with naked seeds, the 

 other as the angiosperms, or plants 

 with encased seeds. Open carpels (fig. 

 153) 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. 



282. The closed pistils of angiosperms are usually distin- 

 guishable into (i) an enlarged basal part, the ovulary* 



* This part was early called the ovary (a name which is still in general 

 use), meaning the organ which produces eggs, under the impression that 



I. W 



b 

 Fig. 153.— a young cone- 

 scale of Scotch pine show- 

 ing the two ovules ; the 

 latter halved parallel to 

 the scale, showing the 

 body of ovule and the pro- 

 longed integument forming 

 the micropyle, m.. The 

 scale .is attached at b. 

 Magnified about 8 diam. — 

 After Keraer. 



