148 



GROWTH AND WORK OF PLANTS 



indicates that it is composed of four parts which are united to 

 form a compound ovary. The ovules are numerous and occur 

 in two rows. The style is longer than the calyx tube and is well 

 shown in the dissection of the flower. The 

 stigma consists of four short, nearly cylin- 

 drical lobes at the apex of the style. In 

 the flower bud these are erect, approximate, 

 and project a little above the convolute 

 petals. Here the inner faces of the anthers 

 are pressed closely against the lower half 

 of the outer face of the stigmas and deposit 

 the pollen on them as described above. 



The four parts of the ovary and the four 

 lobes of the stigma indicate that the pistil is 

 madeupof four parts, or carpels, which have 

 become united into one compound pistil. 

 All of the parts of the flower, therefore, 

 of the evening primrose are m fours. 



240. One species of the evening prim- 

 ^^j^^H^* rose, (Enothera lamarkiana (Lamark's 



.^"MR evening primrose), has become celebrated 



I^Hf through the experiments of the Dutch 



Pfl botanist, DeVries, for the sudden varia- 



4IPP tions which appear in plants grown from 



the seed, giving rise to distinct forms. 

 These forms are regarded as elementary 

 species, and as indicating one method of 

 the evolution of new species. 



Fig. 109. 



Photomicrograph of pollen 

 of evening primrose, showing 

 threads which hold the grains 

 in loose masses. 



Butter and Eggs. 

 (Linaria vulgaris = Linaria linaria.) 



241. This plant occurs by roadsides and in waste places. It 

 is from one to nearly three feet high (3-9 decimeters), branched, 

 with linear leaves. The leaves are mostly alternate, but are often 

 grouped on the stem, two, three, or four arising close together 

 on the stem and almost opposite or verticillate. 



