296 



PLANT LIFE. 



it. At the same time the neighboring leaves are stimulated 

 to increased growth. 



In fernworts the sexual plant is stimulated by the growth 



of the embryo within it, and enlarges considerably. 



But it is soon outgrown by the young sporophyte, 



to which it supplies nourishment until leaves are 



produced and it is able to feed itself (figs. 76 77 



78). 



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

 velopment of the embryo is uninterrupted until 

 a mature sporophyte is 

 formed. In seed-plants 

 the embryo develops to a 

 certain stage, and then 



Fig. 338. — Development of the embryo sporophyte of a moss (Funaria hygro- 

 metrica). A, longitudinal section of the ovary, b, b, /i, shortly after fertilization 

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

 and /' the b isal, or foot ; b, 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, _/", de- 

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

 /", 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 ; A, the 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. 

 A^ magnified 500 diam. ; B and C about 65 diam.— After Sachs, 



