296 



PLANT LIFE. 



it. At the same time tlie neigliboring leaves are stimulated 

 to increased growth. 



Ill leriiworts the sexual jilant is stimulated by the growth 



of the eiiibr)0 within it, and enlarges considerably. 



l!ut it is soon outgrown by the young sporophyte, 



to which it supplies nourishment until leaves are 



pro(Uiced and it is alile to feed itself (figs. 76, 77, 



7S) 



402. Seed. — In all but the seed plants the de- 

 \elopinent of the embryo is uninterrupted until 

 a mature sporojiliyte is 

 formed. In seed-plants 

 the embryo develops to a 

 certain stage, and then 



Fig. 338. — I'eveli.ipinenL of the embryo sporophyte nf a moss (Fimaria Jiygro- 

 ineirica). A^ longititdinal section of the ovary, /', l\ /;, shortly after fertilization 

 of egg which has developed into the embryo, of which y is the apical growing point 

 and f' the b isal, or foot ; /', b. body of ovary ; h, the base of the neck, B, longi- 

 tudinal section through apex of stem and leaves. Two ovaries are seen \ one has 

 failed of fertilization ; the other, c-, has enlarged to accommodate the embryo, y, de- 

 veloping inside it ; /;, its neck, now withered. C^ longitudinal section of same, older; 

 y the embryo has grown downward into the apex of stem ; the ovary, c. has still 

 further enlarged and indeed outgrown the embryo, forming a bladdery case around 

 its base and elsewhere a close sheath for it ; /; , tiie neck. Around the embryo, where 

 it enters the stem, the latter has grown up as a sheath to whose edge the base of 

 ovarv is still attached. A little later the ovary will be torn off at this point and will 

 be lifted on the elongating sporophyte as a dry membranous sheath, the calyptra. 

 W, m.ignilicd 500 diain. ; B and <.' about K^'i, diam. — After Sachs. 



