82 THE BOTANICAL MAGAZINE. LVoi. xxxiv. No. 402. 



Results. 



After three weeks in the culture jars the plants of the poorest 

 cultures appeared to be about to die and it was therefore decided to 

 end the experiment, although many cultures still seemed perfectly 

 healthy. Final observations were made on February 20. 



No cases of Tottingham's " magnesium injury " were observed in 

 any of these 3-week cultures, although the control solution is known 

 to produce mild forms of this physiological disease under certain 

 climatic conditions. Perhaps the low evaporating power of the air 

 and the weak sunlight of our experiment may explain the freedom of 

 our cultures from any of the recognized symptoms of this disturbance. 

 The best plants of the incomplete solutions would have been considered 

 as very satisfactorily grown but for the presence of the still better 

 control plants. The poorer cultures were characterized by smaller 

 plants, with less sturdy stems and with many leaves that were partly 

 or wholly yellow or even dry. In order to obtain comparative nu- 

 merical values for the various solutions each culture was given a 

 relative score value, by inspection, for each of five different observation- 

 al criteria. The plants were not weighed _ The five observational 

 criteria employed were: total height (H), leaf condition (L), sturdiness 

 of stems (S), root branching (Rb), and length of main roots (Rl). 

 Total height denotes the distance from the seed to the extreme tip of 

 the plant, the leaves being extended upward. Leaf condition takes 

 account of the yellowness of leaves and the amount of dead foliage. 

 By sturdiness of stems is meant mainly the apparent stem diameter at 

 the base of the plantlet. Root branching denotes the frequency of 

 branching of the roots. 



For each of the three criteria referring to tops the plants were 

 classified into three groups. The cultures of the best group were each 

 given the score value 1 ; those of the medium group, 2 ; and those of 

 the poorest group, 3. The same plan was followed for the two root 

 criteria, but the roots of certain cultures were so very poor (being all 

 dead or nearly so, and without considerable growth since the plants 

 were placed in the jars) that a fourth group was established in these 

 cases, and the cultures of this group were given the score value 4. 

 The control plants were given the value 1 for every criterion, there 

 being no case where any culture in an incomplete solution surpassed the 

 controls, which were very satisfactorily consistent among themselves. 



It is to be noted that unity represents comparative perfection in 

 growth and that greater numerical values (2, 3, 4) represent successive 



