CH. Vl] GRAND PERIOD. 147 



(173) Distribution of growth in flower -stalks, etc. 



For this purpose the scape of the cowslip {Primula 

 veris) is useful : select a straight-growing stalk, of which 

 the flowers are still in bud, gather it carefully (by cutting, 

 not by pulling), and mark it at intervals of 5 mm. Keep 

 it in a corked test-tube, with a little water at the bottom, 

 for 12—18 hours. 



Vigorously growing shoots of valerian may be treated 

 in the same way, i.e. cut and grown in damp air. 



Plants of Phaseolus in pots, having 2 or 3 internodes 

 developed, are also useful : the marked internodes should 

 not be cut, but left on the plant. 



Here as in the case of the root we get evidence of the 

 " grand period " ; the youngest part of the stems has 

 grown but little, then comes a region where growth is 

 more vigorous, and further back growth again becomes 

 less marked. The maximum of growth will probably be 

 at a region which was originally 50 mm. from the apex. 



(174) Grand period; time observation^. 



The grand period may be observed with bean roots, 4 

 or 5 being measured simultaneously. The experiment 

 should be started when the roots are 5 mm. in length, 

 and the length measured from a mark on the cotyledon. 

 A measurement is to be made every day at a given hour. 



Or a scale may be fixed parallel and close to the root 

 and the daily increment noted by reading off the position 

 of the tip of the root on the graduations. 



^ Sachs, Text-hook of Botany, Ed. ii. p. 817. 



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