﻿GERMINATION AND GAMETOPHYTE OF FERNS. 



119 



heliotropic By shifting the culture of Gymnogramme about 

 90°, a bending of the prothallia was observed in a direction 

 toward the hght, while the rhizoids turned from the light. 



Some work upon the effect of different intensities of light 

 upon the prothallia and reproductive organs was done by 

 Prantl in 1879. He reported that in weak light only anther- 

 idia were developed upon the prothallia. His work was with 

 Aneimia phyllitidis, Polypodium vulgare, Osmunda regalis, 

 and Aspidium filix mas. However, he did not give the in- 

 tensities of the light to which he subjected the prothaUia. 



Klebs' work in 1893 is verified in the main by my results. 

 By weak light he obtained branching prothallia with adven- 

 titious growths and with Pteris aquilina he secured a thread- 

 like growth, resembling that of Trichomanes normally. In 

 strong light heart-shaped prothallia were produced which 

 bore both archegonia and antheridia. 



Furthur work along the line of my investigation is that of 

 Heim. He experimented with strong and weak white light, 

 as well as yellow, blue and violet rays of the spectrum. In 

 strong light he grew heart-shaped prothallia that produced 

 both archegonia and antheridia. He reports the best growth 

 of prothallia in daylight reduced 20-25%. In weakened 

 light, but he does not say how much, elongate prothallia were 

 produced which bore both archegonia and antheridia. The 

 cultures in yellow light grown by him produced long and 

 narrow prothallia with antheridia but no archegonia. 



The blue and violet rays of the spectrum were the same as 

 the reduced light, slackening the growth and producing ad- 

 ventitious prothallia. His results are of interest because the 

 yellow light had the same effect as white light of tolerably 

 small intensity in producing only antheridia. Here I wish to 

 say that my cultures producing antheridia remained so for 

 about six months, with no sign of archegonia upon them. 



The effect of nourishment upon the archegonia and an- 

 theridia was worked upon by Prantl in 1881 with the result 

 that the archegonia could be suppressed by nourishment lack- 

 ing in nitrogen. 



This is interesting in that it shows that other factors than 

 light may enter into the problem. It is very probable that 



