146 



MANUAL OP BOTANY 



contain both micro- and macrosporangia. In Marsilea there is 

 in each a single row of the latter in the middle, and a double 

 row of the former on each side of it. In Pilularia the arrange- 

 ment is not so definite. 



The sporocarp is 

 made to rupture by the 

 mucilaginous character of 

 the internal tissue, which 

 absorbs water and causes 

 the wall of the sporo- 

 carp to split. In Pilularia 

 the rupture begins at the 

 apex, in Marsilea it takes 

 place along the side. In 

 the sporocarp of the latter 

 is a band or ring of mu- 



FiG. 904. 



Fig. 905. 



Fig. 904. Transverse section 

 of the sporocarp of Pilu- 

 l^aria glohulifera. After 

 Henfrey. 



cUaginous tissue, to which 

 the walls of the chambers 

 containing the sori are at- 

 tached. When the sporo- 

 carp ruptures by the swell- 

 ing of this ring, the latter 

 protrudes through the 

 opening, and still swelling 

 drags out with it the sori 

 in a kind of string or chain 

 [fig. 905, B c). When free 

 from the sporocarp the 

 walls of the sori-chambers 

 and those of the sporangia disintegrate, setting free the spores. 



The spores in this group of plants are characteristic. Instead 

 of possessing only two walls and lying free in the sporangia, as 



Fig. 905. Marsilea scdvatrix. A. A sporocarp 

 (natural size). B. A sporocarp whicll has 

 burst its water and is protruding its gelati- 

 nous ring. After Hanstein. c. The ring 

 ruptured and extended, showing the sepa- 

 rated *ori, S7'. D. A sorus showing macro, 

 sporangia and microsporangia. E. A sorus 

 from a ripe sporocarp. After Sachs. 



