I-"ig. 1. Fern prothalli five months old, grown 



from spores on a turn-table revolving four 



times a minute. 

 Fig. 3. Fern prothalli of same age, from same 



lot of spores, receiving light fmm one side 



only. 



Fig. 2. Fern prothalli five moutlis filrl, grown 



from spores on a turn-taltle revolving four 



times a minute. 

 Fig. 4. Fern prothalli of same age, from same 



lot of sfH.ires, receiving light from one side 



only. 



