NOTES ON THE LIFE HISTORY OF THE MOSSES. 



>HE great majority of mosses mature their fruit in autumn or 



winter so that the spores are ready for germination in the 



spring as soon as the proper conditions of moisture and tem- 

 peratu re arrive. When this time comes, the spores, which have been 

 scattered by the wind and the jostling of small animals, burst their 

 brown coats and send out delicate threads (fig. 2). These threads 

 are of two kinds, those that are at the surface of the substratum 

 such as those of the slender Pogonatum (fig. 1) ; these form the 

 protonema, a tangle of green threads that might easily be mis- 

 taken for Algae. Those which grow down beneath the surface 

 are called rhizoids and serve the purpose of roots. This distinc- 

 tion between protonema and rhizoid is more apparent than real 

 as each may develop the other and very often does so. 



The protonema goes on growing like an Alga for a con- 

 siderable time until it has reached the proper stage of develop- 

 ment, when the first moss bud is formed (fig. 3), on some favor- 

 able portion of the protonema by the repeated division of a single 

 unfertilized cell. Thus it will be seen that the whole moss plant 

 thus far and including the protonema corresponds to the prothal- 

 lium of the fern. 



Fig. 1— Protonema of Pogonatum tenue. Fig. 2— Germinating moss spore 

 1 After Goebel ). Fig. 3— Young moss plant starting from protonema. 

 Fig. 4— Stomata and cells of base of outer (exothecial 1 wall of capsule of 

 of Polytrichum commune. Figs. 2 and 4 are magnified about twice as 

 much as 1 and 3. 



As no doubt our readers all know, the ferns have what is 

 called an alternation of generations, the prothallium represent- 



2 



