51 

 Yegetative Reproduction of Protonema. 



(1) Certain rhizoids swell at their apices and form 

 multicellular tuberous structures. The cells fill 

 with oil and resting gemmce are formed. These 

 last through the winter, germinate in the follow- 

 ing spring and form a fresh crop of protonema. 



(2) A711J single cell of leaf or stem of the moss 

 plant may grow out and form a protonema. 



(3) The whole structure dies away in the autumn 

 with the exception of the rhizoids, which germ- 

 inate in the following spring, and form a new 

 protonema. 



DEVELOPMENT OF MOSS PLANTS. 



Little swellings appear on the lateral branches 

 of the protonema. Each grows rapidly by means of 

 a three-sided apical cell and forms the moss plant 

 bud. Each segment cut off by the apical cell bulges 

 out and forms a leaf. 



The Leaves are small, sessile, and broad at their 

 insertion. Each lamina is only one cell in thickness. 

 The midrib consists of a compact mass of elongated 

 cells. Stomata are never found. 



The Stem is roughly triangular, and shows an 

 epidermis not well defined, an outer cortex of small 

 thick-walled cells which passes over into an inner 

 thin-walled cortex. The central cylinder consists of a 

 mass of small, thin-walled cells, which corresponds to 



