T r u e . Notes on the Physiology of the Sporophyte etc. 37 



that in all stages of growth open to study this was true. Ac- 

 cordingly, to more accurately define this zone, it was necessarv 

 te remove tlie calyptra. After a number of failures dne to the 

 great delicacy of the tissues in the end of the yoiing sporophyte, 

 it was found possible to remove this structiire and fix dots of 

 India ink at dose intervals along the apical region. Measure- 

 ments made at intervals of twenty-fonr hoiirs thereafter showed 

 that the zone of elongation was limited to a space within 2 mm 

 from the apex. most rapid growth being found about 0.8 mm 

 from the tip. The young seta was found to have reached its 

 complete diameter at any given 23oint as soon as its growth 

 in length was eompleted. The diameter near the base 

 averages about 0,15 mm and about 0.14 mm near the base of 

 the capsule. 



In a number of young sporophytes from which the calvp- 

 trae had been removed, sharp curvatures appeared, resembling 

 very strongly the traumatropic curves seen in roots (-l). These 

 curvatures were probably due to slight unavoidable injuries in- 

 liicted in removing the calyptrae. To shghtly infiict a wound 

 near the apex was found to produce similar results in erect spo- 

 rophytes from which the calyptrae had been successfully remo- 

 ved. Decapitation experiments seemed to show that the percep- 

 tive region lies in the immediate apex of the sporophyte. 



Having traced roughly the course of the elongation of the 

 sporophyte and its distribution as seen in Funaria, attention was 

 directed toward determining the infiuences bringing about the 

 well - known curvature of the seta seen in Funaria and of 

 Mnium. 



Mnimn showed itself verv sensitive to conditions of li^ht in 

 its natural habitat as indicated by the uniformit}^ with which 

 the individual sporophytes of a turf assume their positions with 

 regard to their environment. Since Funaria &hovfB, itself to be 

 less acurately directed. Mnium was selected for these experiments. 

 Pot cultures were exposed in various positions to the action of 

 gravity and light in the liope of ascertaining whether light is 

 the sole directive influence, as indicated bv Wichura. 



On April 11 at 11 : 45 a. m. a pot of Mnium having 30 young, 

 erect sporophytes was placed in a dark box in such a manner 

 that the perpendicular sporophytes were subjected to lateral Illu- 

 mination through a hole two inches wide bv four inches Ions: 

 at the level of the culture. The pox was placed near a south 

 window in strong diffused light. 



Twenty-four hours later. eight of the sporo])bytes were in- 

 flinefl about '20 '• from the perdendicular toward the soiu'ce of 

 light. Ijy means of a bend within or at the base of the ca- 

 lyptra. 



After another twenty-fotir hours, iifteen individuals had made 

 similar curves toward the light. On April 16, about 120 hours 

 fr<;m the beginning of the experiment, all but three showed piain 

 inclination. It was noted that in every case, the more advanced 



