TEXDEIL-BEAKKRS. 



65 



Legumixos.e. — Pisu-m sativum. — The common Pea was the sub- 

 ject of a valuable memoir by Dutrochet*, who discovered that 

 both the interuodes and tendrils revolved in ellipses. The ellipses 

 are generally very narrow, but sometimes approach to circles : I 

 several times observed that the longer axis slowly changed its 

 direction, which is of importance, as the tendril thus sweeps a 

 much wider circuit. Owing to this change of direction, and 

 likewise to the movement of the stem towards the light, the 

 successive irregular ellipses generally form an irregular spire. 

 I have thought it worth while 

 to annex a tracing of the course 



Fie:. 6. 



Diagram showing the movement 

 of the upper internodes of the com- 

 mon Pea, traced on a hemispherical 

 glass and transferred to paper; re- 

 duced one-half in size. (Aug. 1st.) 



pursued by the upper inter- 

 node (the movement of the 

 tendril being neglected) of a 

 young plant from 8.40 A.M. to 

 9.15 p.ir. The course was 

 traced on a hemispherical glass 

 placed over the plant, and the 

 dots with figures give the hours 

 of observation ; each dot was 

 joined by a straight line : no 

 doubt these lines, if the course 

 had been observed at shorter 

 intervals, would have been all 

 curvilinear. The extremity of 

 the petiole, where the young 

 tendril arises, was 2 inches 

 from the glass, so that if a 

 pencil 2 inches long had been 

 in imagination affixed to the 

 petiole, it would have traced 

 the annexed figure on the 

 under side of the glass ; but 

 it must be remembered that 

 the figure is here reduced one- 

 half. Neglecting the first great- 

 sweep towards the light or 

 window, the end of the pe- 

 tiole swept a space 4 inches »• i 30 

 across in one direction, and 3 inches in another, 

 grown tendril is considerably above 2 inches in length, and as (Ik 



* Comptes Kcndus, torn. xvii. 1813, p. 989. 



Side of room with window. 



h. m. 



1. 8 46 A.M. 



2. 10 „ 



3. 11 „ 



4. 11 37 „ 



5. 12 7 p.m. 



6. 12 30 „ 

 1 „ 



h. m. 

 0. 1 66 P.M. 



10. 2 2"> „ 

 11.3 „ 



12. 3 30 „ 



13. 3 48 „ 



11. 4 40 „ 

 15. 5 5 „ 



h. m. 



18. .". L'-"> l'.M. 

 17. 5 50 „ 

 is. f, I'.", ., 

 lit. 7 0., 



20. 7 45 ,, 



21. 8 30 „ 



22. 9 15 „ 



As a full- 



