2o8 STRUCTURE AND LIFE HISTORIES 



leafy-shoot, and in others the protonemata, may give rise 

 to special small bodies, called gemma, which may become 

 separated from the parent plant and give rise to new plants 

 (Figs. 150 and 151). Gemmae will be illustrated more 

 fully in the liverworts to be discussed in the next chapter. 

 191. Comparison with the Fern. — By comparing Sphag- 

 num with a fern several points of interest are brought 

 out. In the first place, we learn that, while the "fern- 

 plant" with which we are famihar is a sporophyte, the 

 sphagnum-plant is a gametophyte. In the second place, 

 while the sporophyte of the fern is at first dependent on 

 the gametophyte for its nutrition, the sporophyte soon 

 becomes entirely independent, and the simply organized 

 gametophyte perishes; while in sphagnum the sporo- 

 phyte is the much more simply organized, and is depend- 

 ent upon the gametophyte for nutrition throughout its 

 entire life. In their mode of reproduction, however, the 

 two plants are very similar, each producing haploid 

 gametes of two sexes, male and female, that need to fuse 

 in fertilization; the product of fertihzation (zygote) being 

 diploid, and producing a spore-bearing phase; and the 

 spores, haploid again, through reduction, giving rise, 

 without nuclear and cell-fusion to the haploid gameto- 

 phyte. In each case, in the Ufe-cycle, gametophyte 

 alternates with sporophyte, fertilization with reduction, 

 gametes with spores, haploid cells with diploid. What 

 takes place in the cells between fertihzation and reduc- 

 tion, and between reduction and fertilization? This is one 

 of the many fascinating problems in botany still awaiting 

 solution. There is only one way by which the answers 

 to these problems may be ascertained; namely, by accu- 

 rate, persistent, painstaking observation and experiment. 



