ULOTRICHALES 



49 



veloped much farther, especially in its mode of sexual reproduction, 

 because it is anisogamous with elongate antherozoids and large 

 round ova. 



MoNOSTROMACEAE : Monostroma {mono, single; stroma, layer). 

 Figs. 36, 37. 



The thallus develops as a small sac, which in most species 

 ruptures very early to give a torn plate of cells one layer in thick- 



O^x 



R=-^D 



ULOTHRDC Etc. nONOSTROHA 



Fig. 36. Diagram to illustrate the three different types of life cycle found in the 

 Ulotrichales. i^D = place of reduction division in life cycle. 



Fig. 37. Monostroma crepidinum. A, plant ( x |), B, cells of thallus ( x 200). 

 C, transverse section of thallus ( x 200). D, M. Lindaueri, plants ( x f ). (After 

 Chapman.) 



ness, the cells often being arranged in groups of two or four. In 

 M. Grevillei the thallus only ruptures in the adult stage, and traces 

 of the original tubular form can also be seen in adult plants of 

 M. Blytii, whilst in M. Lindaueri the sac appears to remain entire. 



CSA 



