;; I combe, Sensitive Life of Asparagtis plumosim. 



toward the horizontal, and since there is no torsion of the central 

 axis aticr displacemenl from its former position, it follows that 

 the plagiotropic shoot is radial and not dorsiventraL Unlike mosl 

 plagiotropic skoots, that of Asparagus does no1 become plagiotropic 

 tili near cessation of growth. One may invert the plant at any 

 time withont causing the tips of main axis or branches to leave 

 their horizontal {>osition. This absence of dorsiventraJity is evident 

 in appearance as well as in behavior. 



In the preservation of its radial condition, Asparagus resembles 

 rhizomes, 1 ) runners of Fragaria vesca % ) and Halms caesius.*) 



III. Effect of Light on Diageotropism. 



The matter of the partieipation of light in the assumption 

 by aerial shoots of the plagiotropic position is not at present in 

 a satisfactory condition. Thus Czapek 3 ) reports the shoot of 

 Glechotjift hcthriiceti as horizontal in the dark, while both Oltmans 4 ) 

 and Maige 5 ) report only the older shoots of this plant as horizontal 

 in the dark. and State that the spring* or young shoots grow ver- 

 tically upward in the dark. Czapek 3 ) reports the shoots of 

 Lysimachia numularia as Yertical in the dark. horizontal in the 

 light; while Oltmans 4 ) finds these shoots vertical in dark and in 

 weak light, horizontal in strong light; and Maige 6 ) finds them 

 rising to the vertical position when transferred from diffussed to 

 direct sunlight. Illustrations of this sort could be multiplied. But, 

 as Pfeffer 6 ) points out, these differenecs would in large measure 

 disappear, had all authors given attention as have Oltmanns and 

 Maige, to the physiological State of the material they worked 

 with — had they worked with plant — members of the same 

 stage of development, and had they used the same intensities of 

 illumination. 



The earlier writings 7 ) on the causes of change from the or- 

 thotropic to the plagiotropic position were wont to refer the be- 

 havior to a variety of responses, dilfering in different plants, such 

 as negative heliotropism, positive geotropism, photonasty and 



l ) Elfving, Über einige horizontal wachsende Rhizome. (Arbeit, bot. 

 Inst. Würz. IL 4ö9.) 



2 j Czapek, Über die Richtungaursachen der Seitenwurzeln und einiger 

 anderer plagiotroper Pflanzenteile. (Sitzber. Wien. Akad.. Math.-naturw. Kl. CIV. 

 Abt. 1. 1895. p. 1197.) 



3 ) Czapek, 1. c. 



*) Oltmans, Über positiven und negativen Heliotropismus. (Flora. 83. 

 1897. p. 1.) 



5 ) Maige, Recherches sur les plantes rampantes. (Ann. Sei. Nat. Ser. 8. 

 VII. 1900. p. 249.) 



»t Pfeffer. Pflanzenphysiologie. Bd. II. 1904. p. 677. 



7 J Frank. Die natürliche wagcrechte Richtung von Pflanzenteilen. 

 Leipzig 1870. — Sachs, Übar orthotrope und i>luyiotrope Pflanzenteile. (Ar- 

 beit, bot. Inst. Würz. II. 1879. p. 220. j — Czapek. 1. c. 



