VEGE TA TIVE REP ROD UCTION. 



193 



eluding the mossworts, fernworts; and seed plants, the spore 

 case is always formed of two or more spore-producing cells, 

 surrounded by a covering of cells (one or more layers) which 

 do not produce spores. These spore cases may be developed 



Fig. 146. Fig. 147. 



Fig. T46. — Longitudinal section of the simple spore case of a mold (Mzecor). The aerial 

 hypha, A, has partitioned off a cell, j, within which spores are produced. The walls 

 of this spore case are studded with needle crystals of calcium oxalate. The partition 

 protrudes far into the spore case. Magnified 260 diam.— After Kerner. 



Fig. 147. — Longitudinal section of the stem, j, of a moss gametophyte, hearing leaves, 

 6. Embedded in the stem is the sporophyte, consisting of a stalk, st, and a compound 

 spore case, of which w is the waif, formed of a sheet of cells, enclosing the spores, 

 sp (contents not shown). Magnified loo diam. — After Hofmeister. 



either from superficial or from internal cells. As a conse- 

 quence, the mature sporangia will be either free or more or 

 less enclosed within the tissues of the organ by which they 

 are borne. 



273. The sporophyte. — Among the mossworts, fernworts, 

 and seed plants reproduction by spores has become so fixed 

 and important that one stage in the plant is devoted espe- 

 cially to producing them. This phase is different from that 

 producing sex cells, the difference becoming greater the more 

 complex the plant. The stage set apart for spore production 

 is called the sporophyte. In the mossworts the sporophyte 

 has very little green tissue, and therefore carries on little 

 nutritive work, but depends for its supply of food chiefly 



