130 



until a protonemal thread of two to five cells has been formed. The dififer- 

 eutiatlou of an apical cell or group is late and irregular, resulting in un- 

 symmetrical growth. The marginal cells show unusual growth, produc- 

 ing variously formed outgrowths, sometimes bearing antheridia and oc- 

 casionally producing extra growing regions which may even become inde- 

 pendent proliferations. 



With reference to drought resistance the following facts have been 

 noted : Allowing a culture to become dry for one or two days in the normal 

 air of the greenhouse seems in no way to injure the plants beyond check- 

 ing growth during the dry period. One culture left iu dry air with slight 

 additious of water once a week slutwed nearly all the lu-othallia alive and 

 in good condition after a period of threc^ uionths. 'J'lie major ])art of thf' 

 plants of another culture are iu good shape and have produci'il a uumber 

 of sporophytes although snb.jecte<l to such ii-rei;ulai' moisture <<iiiditions 

 for a period of nine montlis. Iu a culture leceiving only air which had 

 been dried by jmssiug tlirougl> iiurt^ glycerine, most of the jirothallia were 

 in sjood condition after four weeks and a few sui-vived such treatment for 

 a i)eriod of six weeks. 



In conclusion, the two s])ecially iiiijiortant a(la])tive features are, the 

 unusual power of promiscuous growth of prothallial cells, aud the aldlity 

 to I'esist extreme desiccalitHi iu iiitciMuitteut iktIoiIs. 



