Certain Reactions of Biocolloids and Cell-masses. 67 



Several- variations are apparent, but perhaps the relations of greatest 

 importance are those which may be expressed by saying that the 

 imbibition of dried specimens is five times that of Uving material in 

 distilled water, only fom- times in nutrient solution, over six times in 

 potassium nitrate, over seven times in magnesium sulphate, less than 

 twice in calcium nitrate, and over four times in dipotassium phos- 

 phate. It is to be noted that when a section of living tissue is dehy- 

 drated it is not possible to restore the cell-colloids to their original 

 condition simply by swelling. This is due chiefly to the fact that, as 

 desiccation proceeds, the salts, acids, sugars, etc., in the hquids are 

 concentrated until finally they are fixed by the soHdifjdng proto- 

 plasmic gel in this condition. Rehydration must then take place as 

 in a salted colloid with the sugars in a concentration in which they 

 may modify imbibition. 



Petioles of young leaves of Phytolacca, with a thickness of 3 mm., 

 swelled 4.2 per cent in distilled water and an equal amount in potassium 

 phosphate, 5 per cent in magnesium sulphate, 3.3 per cent in calcium 

 nitrate, and 2.5 per cent in the nutrient solution. The equivalence 

 or uniformity of the material was in doubt, however, and the test was , 

 not extended to dried sections. 



The 4-angled stems of Mentha spicata offered certain mechanical 

 advantages, and the intemodes near the apex of the stem which were 

 half-grown and with a thickness of 3 mm. were selected. Trios of 

 sections 3 or 4 mm. long were tested with distilled water, culture 

 solution, and its components. The swelling of fresh specimens was 

 very sHght, varying from 0.05 to 0.1 mm., and no safe comparisons 

 could be made. Dried sections came down nearly half of their original 

 dimensions, and when a series was swelled in distilled water the in- 

 crease was but 12.9 per cent and in hundredth-normal citric acid 6.4 

 per cent, while in hundredth-molar sodium hydroxid the increase was 

 19.3 per cent. These results indicate that the plant colloids were in 

 an acidified condition, the swelhng in water and in acid being conse- 

 quently small, while that in alkali was a swelhng in a neutralized or 

 nearly neutralized condition. The dried series in the culture solution 

 and its components gave swellings of 16.8 per cent in distilled water, 

 almost no swellings in nutrient solution (due to defective wetting 

 by the Uquid), 19.3 per cent in potassium nitrate, 12.6 per cent in 

 magnesium sulphate, 9.6 per cent in calcium nitrate, and 4.8 per cent 

 in dipotassic phosphate. The swelling of dried sections presents some 

 possible sources of error in the limited surfaces presented for absorption 

 which may be "waterproofed" in some cases, while in other instances 

 the sections collapse or do not swell toward their original form. 



Direct effects of the waters of bogs and swamps in producing modi- 

 fications of growth, departures in structure and form, and in influenc- 

 ing general nutrition are well estabhshed and have long been known. 



