MUSCI. 



171 



when it proceeds from gemmae. The only exception is in the few cases in which leaf- 

 buds become detached and begin to develope immediately (see too Fig. 124, A and ). 

 In describing the different cases, it should be noticed first of all, that both the 

 protonema that springs from the spore and the leafy stems formed on the protonema 

 are capable of propagation in more than one way. The original protonema is an 

 organ of multiplication, inasmuch as its branches bear several, often very many, leafy 

 stems one after another or simultaneously; and sometimes the single cells of the 

 branches of the protonema assume a globular shape and separate from one another ; 

 their cell-walls grow thicker and they lie dormant for a time, as mFunaria hygrometrica, 



FIG. 124. Small tuberous bodies formed on the protonema produced on the stem ^ of a Barbula, which have 

 germinated by the development of single superficial cells into new protonemal filaments; other cells (one in A, one in 

 C and two in B) have become directly the apical cells of a moss-bud (Kn, A, B), and in C and B have grown already 

 into leafy stems ; j stalk-cell, f lateral branch with limited growth. After Miiller (Thurgau). 



and probably develope new protonema-filaments at some future period. But a secondary 

 protonema may also be produced from every rhizoid that is kept moist and exposed 

 to the light (Fig. 116 and Fig. 123 /); in the case of Mnium, Bryum, Barbula and 

 other species it is sufficient to keep a turf of Moss with its felt of rhizoids turned up and 

 in a moist condition for a few days to see hundreds of new plants formed on it in this 

 way. Many species of Phascum, Funaria, Pottia, which are apparently annual, are 

 virtually perennial by aid of their rhizoids; the plants disappear entirely from the 

 surface of the ground after they have ripened their spores till the following autumn, 

 when the mat of rhizoids again puts out new protonemal filaments, on which new 



