IRRITABLE RESPONSE 



223 



I find it needs to be kept in the most perfect condition to work properly. 

 A small form, with escapement regulator, suitable only for seedlings or plants 

 of very light weight, is that of HANSEN (Flora, 84, 1897, 353), costing 115 

 marks, but it has serious practical limitations. Recently a new and very 

 different form has been described by NEWCOMBE (Botanical Gazette, 38, 

 1904, 427); it is driven by a small electric or water motor, whose speed is 

 stopped down by suitable worm-gear 

 or pulleys. It has the advantages 

 of simplicity in construction, moderate 

 cost, possibility of connecting several 

 Klinostats in series to one motor, and 

 especially of so much power that any 

 retarding effect due to irregular distri- 

 bution of weight is wholly eliminated. 

 Another electrically driven form of 

 different details of construction has 

 also been described by VAN HARREVELD 

 (Die Unzulanglichkeit der heutigen 

 Klinostaten fur reizphysiologische 

 Untersuchungen, Groningen, Holland, 

 M. de Waal, 1907). This electrically 

 driven type is likely to form the stand- 

 ard instrument for research in the fu- 

 ture. Its need for a constant electric 

 current, or constant head of water, 

 obviously limits its usefulness for edu- 

 cational purposes, and in order to pro- 

 vide a suitable form for educational 

 demonstration, I have designed the in- 

 strument which is supplied among my 

 normal apparatus and is figured 

 herewith (Figs. 61, 62, 63). Though 

 intended primarily for educational use, 

 for which it is ample, it is incidentally 

 entirely suitable for some investiga- 

 tion purposes where light weights are 

 concerned, or where these are carried 

 with the axis vertical. It consists essen- FIG. 61. DEMONSTRATION KLINOSTAT; 

 tially of the works of a powerful eight- Xi. 



day clock, geared to a revolution in 



fifteen minutes (this being the only speed required for educational demon- 

 stration and for most investigation) and enclosed in a practically dust- and 

 moisture-proof case, 16 cm. in diameter. It can be used in any position what- 

 ever, as shown by the accompanying figures. It has been greatly improved 

 over the original form (described in the Botanical Gazette, 37, 1904, 304) 

 by the addition of a ball-bearing shaft which takes the strain from the works, 

 while friction-rollers have been added to the spindle-rod support. The 



