Fig. 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 from one side 



only. 



Fern prothalli five months old, grown 

 spores on a turn-table revolving four 

 times a minute. 

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

 lot of spores, receiving light from one side 

 only. 



