- 242 
BOTANICAL GAZETTE 
[OCTOBER 
was an increase in hard bast. The other species all responded to 
tension by increasing their xylem area. The average thickness of 
TABLE X.—SUMMARY 
No. of 
experiment 
Avi Aver- | Aver- |Average| ,._. |Average 
— i age | age thick. ick thick- | 175 of 
Name of plant ing ead pny beni of hard Pans ee 
eogth) bast | bast bast | bast Pos xylem 
n kg. fibers | fibers | area |cell walls cell walls 
lelianthus es Ls BEE a 7 § mn eae ae 6.70 5 
lianthus annuus | 3 Watine asl’ Gan of sk 4570 5 
felianthus annuus /16, SS eres eaectiaaits sate pore ee 
elianthus annuus |13., Tia wo paiae| Eee arcae Peeerand eboney (Ae Macnee poe 
elianthus annuus 69 SONOS 7% SEC es ee ee 
elianthus $106,520). si: Epi fetes peters Rene 57 Sy 
napis a By F7Ol Se. TR O36) sol. aves 9-39] 3- 
napis alb au 5-330 MEE OE aia ee. 10.51| 2.993} 20 
haseolus Vitpatis 16, 9get S|. BRUogiss COORG oer 
haseolus vulgaris Oe, | ee ae ase NOSE oO 5 -42].-+++- 
Phaseolus vulgaris (eect e) Waseremte | ge Plane oly oo ae adie La eee 
Phaseolus vulgaris ce’ fo. (aeeperee | Reagent) Wein enti be onee abe cos 
Phaseolus S16. 3361. S top Co Beenie Seren wey Maar CS Ei 
Phaseolus vulgaris y As on pee ea es Ops Pees epee oeese bere 
Vinca major is or | ome ane Ee Soren eee Se nee 
2 ajor gS IR cate eran eee eed Mame etry Daren ats cn ec 9c 
Vinca major* Lh, 2 CS Sinea ee paatieeraes peta! paren ome 
Vinca major* i; Rag Rn tess Sy npems Cerne P< 
Vinca major Bogaat os 1276|:.... 7-42 |-2777| 5-77 
Vinca major GOO7Gh 5 os 7] see 6.56 |.2141| 5-09 
Ricinus communis Ags HOOPS e hele ligl pe eee a ed 2759] | eres 
cinus communis |41.220|......|.....|.....|...... 5-99}- +--+ +} 
ubus occidentalis |. 0.1... 1... SOs 210 
Rubus occidentalis | .....|......|..... cee Bae £i9O9) ss os 
Vicia Faba* PALOO SS seen] cele 3 | apa si Boccia terme acti aae ee oie 
Vicia Faba* BO gt a eb see eee 
Vicia Faba 24 OTOL 6s BOBO eee 22.75). +0 
Vicia Faba 20 SOON ss 2 PAID) ste 21.00]..--+- 
Adenine Wibaa to PAG) iis a eee ts Q127|----+° 
Lupinus albus {......|.... i ee ips a ae S000}. ..++: 
* See experiments for explanations of negative results. 
° . . . . : in 
xylem cells walls in Sinapis alba and Vinca major was also greater 
the experimental stems than the controls. 
% 
Conclusion 
The results of the foregoing experiments have convinced the sed 
conclusively that actively growing stems of the herbaceous plant 
investigated and of Vinca major respond to traction along their cat 
tudinal axes, by increasing their breaking strength; also “a ee 
increased development of bast or of xylem, and in most cases by 
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