264 



SEEDLESS PLANTS 



two moistened bits of glass and hold it up to the light, keep- 

 ing the upper surface toward you ; what is its appearance ? 

 Observe a tiny dot near the center of the rhomboidal 

 areas into which the epidermis is divided and compare it 

 with your drawings of stomata (Sec. 16). What should 

 you judge that these dots are ? 



372. Rhizoids. — Wash the dirt from the under side of a 

 thallus and examine with a lens ; how does it differ from 

 the upper surface .-' Observe the numerous rootlike hairs, 

 or rhizoids. What is their color .' Where do they spring 

 from ? These are not true roots, but hairs that have taken 

 upon themselves the function of absorption, and do not 

 imply any actual differentiation of tissues. 



Plant a growing thallus branch in moist earth so that 

 the upper side will lie next the soil and watch for a week 

 or two, noting what changes take place. What would you 



infer from this as to the cause 

 of the difference between the 

 two surfaces ? Would rhizoids 

 be of any use on the upper side .' 

 Stomata on the under side ? 



373. Gemmae. — Look along 

 the upper surface of some of 

 your specimens for little saucer- 

 shaped (in Lunularia, crescent- 

 shaped) cupules or cavities. 

 Notice the border, whether it 

 is toothed or entire, and see if 

 you can tell what the cupules 

 contain. These little bodies, 

 called gemmce, are a kind of bud, 

 by which the plant propagates 

 itself somewhat as the onion 

 and the tiger lily do by means of 

 bulblets. Sow some of the gem- 

 mae on moist sand, cover them with a tumbler to prevent 

 evaporation, and watch them develop the thalloid structure. 



504-507. — Lunularia, a common 

 liverwort : 504, portion of a thallus 

 of about natural size : g,g, gemmse ; 

 505, a fertile plant with fruiting 

 receptacles ; 506, an enlarged sec- 

 tion of one of the fruiting recepta- 

 cles ; 507, portion of a sterile thallus 

 slightly enlarged, showing one of 

 the crescent-shaped gemmse from 

 which the plant takes its name. 



