44 HUMPHREY 



light there is a strong tendency to turn toward the light, and if 

 this is not accomplished by the germ-tube, the further develop- 

 ment of the young plant will at once or gradually assume the 

 direction of positive heliotropism. 



DURATION OF VITALITY OF CERTAIN GREEN OR THIN- 

 WALLED SPORES. 



A failure to germinate the spores of Aneura multijida major 

 after they had been allowed to become several weeks old, 

 induced the writer to prepare a series of cultures to test the life 

 duration of the spores of Aneura^ Radula^ Poi-ella and 

 FegateUa. 



The first spore cultures of all these forms were started on the 

 same day of collection in order to determine whether the spores 

 were ready for germination under normal conditions. Practi- 

 cally all spores germinated in cultures consisting of sterilized 

 earth, Knop's solution and distilled water. I next allowed 

 spores of FegateUa to dry for three days, by placing them on a 

 sheet of paper on the laboratory table. These were then sown 

 in the various culture media. Many of the spores had already 

 germinated within the capsule but these along with all spores 

 still ungerminated failed to show the slightest sign of any 

 recovery after days of constant moisture and favorable light. 

 Later, Professor Peirce demonstrated that one hour's drying 

 under normal conditions was sufficient to kill all spores, and 

 further experiments with the spores of this species were re- 

 garded unnecessary. The spore wall in the case of FegateUa 

 is very thin, allowing rapid loss of the water of constitution, 

 resulting in a general contraction of spore contents and collapse 

 of the spore wall. 



On January 12 cultures were started, sowing spores of Radula 

 complanata collected on the ninth of the same month. Prac- 

 tically all of these germinated within a few days, so another 

 trial was not made till the twenty-eighth of January. Approxi- 

 mately ten per cent, of the spores of this sowing failed to 

 recover, the cytoplasm and other spore contents having con- 

 tracted towards the center forming a brownish mass. 



On February 11 a third culture was started, the spores now 



