108 Jean White: 



In Callitris gunni, Cedrus deodara a.nd Thuja orientalis, there 

 ■\va« a less oonspicuous layer of red tracheides produced on the 

 under siu'face of the main stem and its branches. 



The Cupressus sempervireiis was ako removed from the 

 klinostat on 28th November, 1906. 



During the two months' rotation, there were two stoppages of 

 the klinostat for a possible duration of 16 hours and 3 hours 

 respectivel3^ Examination showed a uniform exceedingly fadnt 

 layer of red wood round the main stem and lateral branches. The 

 Cupressus plant had two similar main i>tems, one of which v.as 

 examined when it was first removed from the klinostat, and the 

 other one after it was removed for the second time. 



The Cupressus plant was replaced on the klinostat on :29th 

 November, 1906, the speed of rotation being changed to one 

 revolution in two minutes. It was kept on the klinostat till 28th 

 December, during which time there was a stoppage of the 

 machine possibly for 30 hours. On examination of the stem, after 

 removal of the plant from the klinostat on 28th December, no 

 red wood was visible. Evidently, therefore, to produce any per- 

 manent impression upon the developing cambial segments, the 

 gravitational stimulus must last at least 1 to 2 hours. One 

 minute's stimulation is either not perceived, or leaves the seg- 

 ment cell in a labile condition, continuallj^ reversed by the 

 completion of each rotation without producing any permanent 

 and definite morphogenic response. 



The pot containing the ('upres>us plant was laid on its side in 

 the glass-house on 25th January, 1907, the upper side of the 

 flower put ))eing marked. It was left in this position till 18th 

 October, 1907. On stripping oft' the bark, a thick layer of 

 red wood, altout 20 tracheides deep, was observed on the under 

 surface of the main steam and lateral branches. 



The above results serve to strengthen Professor Ewart's and 

 Mr. Mason-Jones' conclusions as to the primary stimulus le- 

 sponsible for the production of the red wood, being a gravita- 

 tional one. 



Diameter of the Xijh i/i ]'rss<-/x, (mil 'Jlnrkiirss of 

 Their Walls. 



The diameters of the cavities of the vessels, and also the 

 tliickness of the vessel walls were measured by meaoas of the 



