96 Hydration and Growth. 



The familiar relation much seen in young organs, by which the 

 imbibition is least in the acid and most in water and alkaline solutions, 

 is exhibited. Some interest attaches to this plant from the fact that 

 its expressed and centrifuged juice has been found by Dr. H. A. Spoehr 

 to aggregate and form a fairly firm jelly without concentration, an 

 action probably due to the large proportion of pentosans present. 



Forms of Brodicea native to Tumamoc Hill start into activity late 

 in February and by the end of the first week in March have formed new 

 corms on the crowns of the older ones nearly 1 cm. in diameter, from 

 the apices of which the long, slender leaves extend at a rapid rate. 

 Halves of these corms arranged in the dishes under the auxographs 

 gave swellings at 20° C. as shown in table 73. 



Table 73. 



p. ct. 



Distilled water 5 



Citric acid, 0.01 N 2.7 



Sodium hydroxid, 0.01 M (not completed) 2.2 



Potassium chloride, hydrochloric acid, 0.01 M 2.5 



The carbohydrate material in these organs is starch, and this and 

 the products of its hydrolysis constitute the main components of the 

 cells. The increases noted above are low, that in the alkaline solution 

 being still in progress. The old corms form tapering extensions from 

 the lower surface, which in the earlier stages are made up only of thin- 

 walled cells, filled with the products of starch hydrolysis. These 

 show swellings of 17 per cent in distilled water at the above tem- 

 perature. Two other variations were tried to ascertain whether the 

 young corm jtist formed, having swelling capacities as above, differed 

 in hydration capacity from the older basal corms being emptied of their 

 contents. This was accomplished by setting up a preparation of three 

 plants in which the young corms were seated in place on the older 

 corms. The average height of the preparation was 12 mm. and the 

 increase in distilled water was 9.6 per cent at 20° C. Another set of prep- 

 arations was made, in which older corms from which the young portion 

 had been removed were immersed in water at similar temperatures. 

 The increase in this case was 24 per cent, showing that these structures, 

 in which the accumulated starch was in an advanced stage of hydrolysis, 

 had an imbibition capacity much greater than that of the young corms. 

 The fact must be taken into account that the young corms were firm 

 and sohd to the touch and were to be regarded as in a high state of 

 imbibition, while the old corms had been partially emptied, but were 

 capable of returning to the dimensions of their original turgid con- 

 dition. 



Tangential sUces from the terminal internodes of asparagus tips, 

 bought in the market in Tucson in March, were made to have a thick- 

 ness of about 3 mm., and these gave swellings as shown in table 74. 



