Newconibe, Sensitive Life of Asparagus plumosus. 17 



its negative geotropism up to the cessation of g-rowth. Plants, 

 revolving as here indicated, have in 9 tests when the revolution 

 was stopped before the plants were mature, shown negative geotropic 

 curves in both the main axis and in the lateral branches. 



IL Relation toward Light. 



The main axis of the seedling shoot and of the shoots arising 

 from the rhizome are strongly positively heliotropic from their 

 first appearance above ground to the cessation of growth with the 

 tip in the horizontal position. The lateral branches of lower order 

 than the needles are certainly less responsive to light than is the 

 tip of the main axis, for they are but slowly and slightly deflected 

 from their straight course by one-sided illumination. The lateral 

 branches are under the domination of the 2 Stimuli which cause 

 them to take the horizontal position and their "proper angle" in 

 this horizontal plane, and they are not easily diverted from their 

 reaction to these two factors. The tip of the main axis, on the 

 other hand, will readily bend aside from its straight course in re- 

 sponse to light, even when the diageotropic shoot has unfolded 

 the most of its branches and needles. 



One of the effects of growing these Asjiaragus plants in the 

 dark is to extend elongation enorinously. A shoot that would grow 

 to a total length of 15 or 20 cm in the light will attain an in- 

 definite length in the dark. I have raised several such shoots to 

 a hight of over 200 cm, and discontinued the experiment with no 

 indication of growth ceasing. This striking result in etiolation is 

 accounted for to a limited extent by the greater length of internodes 

 in the dark. The internode length of the main axis of a plant 

 growing in light varies from 10 or 12 mm near the ground to 20 

 or 25 mm just below the first branch. In etiolated shoots, the 

 length of internode varies from 12 mm to 60 mm, but the usual 

 length is 25 to 38 mm. The increased length of internode would 

 account for less than the doubling of the normal length of the 

 plant. Since plants have been grown in the dark to 15 times the 

 normal length, it follows that, in an etiolated plant, there are many 

 more internodes formed. In other words, light, in the case of the 

 normal plant, inhibits growth, speedily setting bounds to its du- 

 ration. The shoots of my earlier preparations that grew to such 

 great hights in the dark were grown in opaque black paper cones 

 or cylinders, the neighboring green shoots from the same rhizomes 

 being left in the light. It was then supposed that these etiolated 

 shoots were supplied with assimilated material from the green 

 shoots, and that we had here the unusual case of a shoot in the 

 dark nursed by a neighboring assimilating shoot. To test the value 

 of this hypothesis, the green shoots of several pots were wholly 

 cut away and the pots were set in the dark. Within a week 

 three rhizomes sent up each a new shoot. These were attended 

 and watched for 6 months, when all plants were still living and 

 had reached hights respectively of 177 cm, 74 cm, and 75.5 cm. 



Beihefte Bot. Centralbl. Bd. XXXI. Abt. I. Heft 1. 2 



