162 CRYPTOGAMOUS OR FLOWERLESS PLANTS. [SECTION 17. 



betx globular or pill-shaped frnit (SPOROCARPS) on the lower part of then 

 leaf-stalks or on their sleuder creeping steins. The leaves of the commoner 

 species of Marsilia might be taken for four-leaved Clover. (See Fig. 520.) 

 The sporocarps are usually raised on a short stalk. Within they are 

 divided lengthwise by a partition, and then crosswise by several partitions. 

 These partitions bear numerous delicate sacs or spore-cases of two kinds, 

 intermixed. The larger ones contain each a large spore, or macrospore ; 

 the smaller contain numerous microspores, immersed in mucilage. At 

 maturity the fruit bursts or splits open at top, and the two kinds of spores 

 are discharged. The large ones in germination produce a small prothallus ; 

 upon which the contents of the microspores act in the same way as iu 

 Ferns, and with a similar result 



496. Azolla is a little floating plant, looking like a small Liverwort or 

 Moss. Its branches are covered with minute and scale-shaped leaves. 

 On the under side of the branches are found egg-shaped thin- walled sporo- 

 carps of two kinds. The small ones open across and discharge micro- 

 spores ; the larger burst irregularly, and bring to view globose spore-cases, 

 attached to the bottom of the sporocarp by a slender stalk. These delicate 

 spore-cases burst and set free about four macrospores, which are ferti. 

 lized at germination, in the manner of the Pillworts and Quillworts. 



(See Fig. 521-526.) 



521 



497. Cellular Cryptogams (483) are so called because composed, 

 even in their higher forms, of cellular tissue only, without proper wood- 

 cells or vessels. Many of the lower kinds are mere plates, or ribbons, 

 or simple rows of cells, or even single cells. But their highest orders 

 follow the plan of Ferns and phanerogamous plants in having stem and 

 leaves for their upward growth, and commonly roots, or at least rootlets, 



FIG. 521. Small plant of Azolla Carolinians. 522. Portion magnified, showing 

 tbe two kinds of sporocarp; the small ones contain microspores ; 523 represents 

 one more magnified. 524. The larger sporocarp more magnified. 525. Same 

 more magnified and burst open, showing stalked spore-cases. 526. Two of the 

 latter highly magnified ; one of them bursting shows four contained macrospores: 

 between the two, three of these scores highly magnified. 



