58 THE THALLUS OF THE GENUS PAKMELIA, 



(I.) The plants were placed in a desiccator over 

 calcium chloride and left for a space of three: 

 months, July to October, 1911. The upper surface 

 and go-nidial layer were the most deeply affected, 

 and the drying of these portions caiised the curling 

 up of the thallus, so as to hide the upper cortex 

 and show the brown underside. At the end of 

 thirteen weeks, the plants, very dry and crumbly, 

 were placed on absorbent paper, in their natural 

 position, and water was poured from a can in a 

 circle round them. The paper conveyed the water 

 to the plants, it was absorbed by their under sur- 

 faces, and in 5-7 minutes from the water reaching 

 them each thallus was green and expanded. 



(II.) The jjlants, now healthy and normal, were 

 divided into two equal portions, and one half 

 was placed on several folds of newspaper- still 

 with a small layer of soil adherent to each thallus, 

 and watered in the same manner as in the first 

 experiment, so that no water was applied to the 

 tipper cortex. The water was su})plied from an 

 ordinary can, tinned over, but rusted in one or 

 two places, so that the only nourishment came 

 from the tap water, the iron and the soil. These 

 plants were health}'- and normal under this treat- 

 ment in January, 1912. 



(III.) The second half of the plants left over from 



Experiment II. were placed in a. ja,panned dish, 



and supplied with tap water, sufficient to cover 



them, which was changed daily. For six weeks 



they remained healthy and unchanged, but at 



the beginning of the seventh week they became 



gummy, as m.arine algi?e do, that are placed in 



fresh water, and assumed an unhealthy, dark 



green tint. Taken from the water and placed on 



soil and paper, and treated as in Experiment II., 



they recovered, but never quite resumed their 



normal appearance. 



In the first experiment, the loss of food matters, other 



than gaseous food— carbon dioxide— was felt most sieverely 



by the algal symbiont, and the shrinkage in the algal 



layer caused the curling inwards and upwards of the 



thallus. The loss ol organic food, saprophytic fluids, did 



not sieverely affect the hyphse, as they had the supply of 



organic food in the gonidia to draw upon. 



In the third experiment the supply of gaseous food 



