166 I'HE BOTANICAL MAGAZINE. Lv.i. xxxiii. n,.. is.-. 



chaiaclcr of the sexual cell," and " along with sex-determiners there 

 must be corresponding sex-inhibitors, for it seems clear that everj' 

 protoplast contains both determiners, but gamete-forming protoplasts 

 produce one kind of gamete. It seems probable, therefore, that every 

 gamete-forming protoplast is equipped with two determiners and one 

 inhibitor." 



The germinated spores are capable of producing both of the 

 " determiners " but the formation of archegonia and antheridia is con- 

 trolf^ by the formative stimuli of the external condition under which 

 the prothaliia are grown. It seems to be that a definite chemical 

 co-ordination is held when the formative stimuli are once released to 

 produce archegonia in such a way as to interfere in some way the 

 liberation of the stimuli of the antheridia formation. But the es- 

 tablished relation may be diverse according to the condition of growth 

 as well as the species of the plant. If it is complete, the formation of 

 antheridia is entirely suppressed and tlie perfect dioecisra results. But 

 if it is incomplete, the fv)rmation of the antheridia is jiossible and 

 monoecism is established. The nature of stimuli seems to be chemical, 

 since the prothaliia grown on the nutrient solutions of low concentra- 

 tion and deficient in nitrogen or some other essential nutrient ele- 

 ments produce no archegonia, and further the light is essential. The 

 photosynthetic product seems to be vitally concerned. 



As already stated, differentiation of meristem is an imjaortant 

 factor in the formation of archegonia. Mere vigorous vegetative 

 growth without establishing the meristem does not induce the differ- 

 entiation and the development of a particular sex and its organs. 



The case of apogamy is of interest. The cases are on record (De 

 Baky: 1878, Heim : 1896, Lang: 1898, Woronin : 1907, Nagai: 1913, 

 Stell : 1915, WuisT : 1917, Stokev : 1918) which sliow that the apo- 

 gamous growth is also negatively correlated with the development 

 of sexual organs completel}^ or partially. 



A mention has already been made on the fact tliat the condition 

 of sex differentiation in a prothallium and in a |)opulation at a given 

 time presents somewhat different problem. Differentiation of sex in- 

 volves two phases, namely qualitative and quantitative and the data 

 elsewhere presented show conclusively that the concentration of the 

 nutrient solution alone exerts a profound influence on both ])hases. 

 Another pha.se tliat needs to be considered is the manner of distribu- 

 tion or variability. It is dear enough that the individual prothallium 

 may be one of the following : 



