444 
Notes . 
that the water is able to pass the air-bubbles and surface tension films in the vessels, 
and yet the films are able to exert a back pressure increasing the resistance to flow. 
Further research must determine whether the explanation given is a true one, or 
whether unknown factors enter into play in the vessels. 
When the walls of the vessels dry, or become covered internally over the whole 
or parts of their length by films of oily or similar substances, a true Jamin’s chain may 
be set up in the vessel (Fig. io). This, when once formed, is difficult to remove and 
interposes a relatively enormous resistance to flow when the vessel is narrow and the 
air-bubbles numerous. Even then, however, the presence of longitudinal pores 
containing water and longer than the air-bubbles may allow water to pass slowly 
even when the films appear to be adherent to the internal wall. The air in dry wood 
vessels always tends to break into shorter or longer bubbles when the wood is soaked 
in water, so that the normal conductivity can only be restored by forcing in water 
under such pressure as either to break the adhesion of the surface tension films 
to the walls of the wood vessels, or to render their attachment more labile. Naturally 
the conductivity restored in this way will be rapidly lost again if the wood is allowed 
to become depleted of water, and even if the supply is maintained by suction, the 
presence of any films of oily or impermeable material on the interior of the vessels 
will tend along with the increasing air-bubbles to produce an ordinary high resistance 
Jamin’s chain. The latter involves an interrupted column of water, rapid upward 
flow requiring a movement of the entire series of air-bubbles and water-columns, 
which is impossible in vessels with imperforate partitions across them. 
On the other hand, the valvular type of Jamin’s chain with a peripheral adhesion 
film of water, allows local feeble pumping actions to be maintained from point to 
point in a staircase fashion. The least resistance to flow is shown when the vessels 
are filled with water, and continuous water-columns may support a tension of over 
200 atmospheres in the absence of air 1 . The transpiring leaves cannot exert the 
tensions required even momentarily in the wood vessels of the tallest trees (150 
metres), since these are very much greater than is usually supposed 2 . 
ALFRED J. EWART. 
Birmingham University. 
ON ENDOPHYTIC ADAPTATION SHOWN BY ERYSIPHE GRAMINIS, 
DC., UNDER CULTURAL CONDITIONS 3 .— In recent papers by the author 
the fact has been pointed out that certain species of the Erysiphaceae are able, 
under cultural conditions, to infect their host-plants vigorously when their conidia or 
ascospores are sown on the cells of the internal tissues exposed by means of a wound, 
although the fungi in question are confined normally to the external surface of the 
epidermal cells. 
The present paper gives the results of investigations carried out in the laboratory 
of Professor Marshall Ward at Cambridge, with the object of ascertaining the details 
1 Berthelot, Ann. de Chimie, xxx, 1852. 2 Ewart, loc. cit., p. 55. 
3 Abstract of a paper read before the Royal Society on April 6, 1905. 
