38 Truc. Notos oll llif I'livsiölotjy of the Sporoplij'te etc. 



sporophytes perform ed this reaction, indicatin^ lliat for a time, 

 tlie yoiing sixirojjliytes are not verv s(;iisitivc to liglil, becomiiii; 

 increasiiigly so until tliey read through a dislinct change intlie 

 distribution of growth, resnlting in the inclination sfon. 



A Mii i i< )n •cuhnve in w hicli i»nly erect sporophyte.s were seen 

 was plaoed on April 11, at 12:00 m, in a horizontal position 

 and illuminated ^vith liglit reflected from the sky in a direction 

 parallel Avith the long axe.s of the sporophytes. After 20 hours 

 several showed sliglit bends near the tips, in different direetions, 

 some upwards, two laterally, others downward.s. On April 13, 

 five out of twenty-two individuals were inclined downwards, 

 three upwards, two laterally, the remainder maintaining the ho- 

 rizontal })osition, presuniably not yet having reached that stage 

 in their development at which they became sensitive to gravity. 

 On April IG, eight sliowed a downward curvature, three pointed 

 obliqiiely downward, two pointed upward, nine were still hori- 

 zontal. Tliree had beeome capable of perception and motion 

 since A])ril 13, and had responded 1:>y a downward curvature. 

 On April 17, ten curved downward, the two laterally directed 

 individuals had changed position so as to point downward, two 

 still pointed upward. On April 19, ;ill had taken a position in 

 wliicli the s[)orophytes pointed downward. 



From this experiment, it appears that for a time the young 

 sporophytes are not perceptive to gravity and maintain for days 

 in a horizontal position an „Eigenrichtung" derived possibly 

 from the relation to the sporophyte. As they beeome capable 

 of perception and reaction, in spite of Illumination ])arallel with 

 their long axes, the rudiments resjDond by curvatures directing 

 tlie apices toward the earth. 



Thus it appears probable that Miihim sporophytes take on 

 the curvature characteristically made in res])onse to geotropic 

 induction. 



In the hope of getting further light on the question of the 

 part played by gravitation anrl liglit. a culture of Mnium was 

 placed in a perpenflicrilar position, illuminated from aliove 1)y 

 diffused light. 



On April 12, all sporophytes were perpendicular, on April 

 13, thirteen out of thirty showed a distinct cui'vature near the 

 base of the calyptra. On April 15, iifteen were still erect, the 

 others showing curvatures varying from a few degrees to as high 

 as 90 from the perjoendicular. On Api'il 18, all were more or 

 less inclined, and invarious radii, indicating no marked directive 

 influence. Here, as bevore, a period of inability to perceive or 

 react is foUowed by perception and reaction. 



From the experiments sketched here in scant outline, it ap- 

 pears probable that the curvattu-e of the seta in the species is 

 due to a growth reaction on the part of the young sporophyte 

 to the Stimulus of gravity. It appears probable, also, in view 



