THE PTERIDOPHYTA : FILICALES, THE FERNS 



545 



'^mm. 



'^^il 



^ m 



I mm 



\ dpi; ■ ^ 

 B 



i 



1' 





^l^^-fli 



Ji^ 



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D 



Fig. 546. — Botrychium hinoria. Stages in meiosis of spore mother cells. A, Heterot^'pic 

 prophase. B, Heterotypic metaphase. C, Late heterotypic anaphase. D, Homotypic 

 telophase showing formation of spore tetrads. The plasmodial ingrowths from the 

 tapetum appear among the developing spores. 



At this stage the embryo becomes free from the prothallus. It continues 

 to produce small immature leaves and thick roots for several years, and it is 

 not until the plant is eight to ten } ears old that it puts up its first green leaf. 

 All this time it lives underground as a saprophyte, without chlorophyll, and 

 except for the growth of the roots it hardly increases in size. This prolonged 

 immaturity is characteristic of the small family Ophioglossaceae. This family 

 includes besides Botrychium the genus Ophioglossum, which is of world- 

 wide distribution, including Britain, and Helminthostachys zeylanica, a plant 

 of south-eastern Asia and Australia. 



