DESSICATION IN PLANTS. 155 



It appears therefore that when ordinary resistant seeds 

 are dessicated the lowest percentage of water which they 

 can contain without their vitality being injuriously 

 affected lies between 2% and 3% of their dry weight, as 

 the percentage is reduced below this amount successively 

 more and more of the seeds are killed. The fact that it 

 seems to be impossible to remove this water, without, at 

 the same time, destroying the vitality of the seed (or 

 plant) , suggests that the water may be associated in some 

 manner, perhaps in a loose chemical combination, with 

 the plasma of the seed. It is very probable, however, 

 that the water held so tenaciously is merely capillary 

 water for it is well known that excessively fine capillaries, 

 such as the molecular or micellar interstices of an 

 organized structure hold water with a very great force and 

 offer a considerable resistance to its loss by evaporation. 

 The fact that the dead seeds lost water more readily 

 might be simply due to an alteration of the molecular 

 structure, caused by the boiling, having taken place, for if 

 the seeds are kept in water at 100°C. just long enough to 

 kill them and no longer, it is found that they lose water 

 when dessicated with but little greater rapidity than 

 normal seeds do. 



What is quite certain, is, that dry but vital plasma 

 cannot possibly be of the same chemical composition as 

 living active fluid plasma on the one hand, or as dead 

 proteid on the other, but is probably intermediate between 

 the two. The change from the fluid or colloid to the 

 solid condition is, of course, a mere physical change 

 directly due to the withdrawal of water, but induces a 

 profound chemical change. Dry protoplasm is perfectly 

 dormant, it can neither respire nor assimilate, add to its 

 substance or diminish it. In the dry condition it is a 

 stable and non-oxidizable chemical compound. According 



