16 HORTICULTURAL SOCIETY OF NEW YORK. 



farinosa is a desert shrub which has been introduced into the 

 xero-montane plantation of the Desert Laboratory at 6,000 feet, 

 being taken from a habitat at 2,500 feet and correspondingly 

 warmer'. It is a winter perennial, however, and its season of activ- 

 ity lies within the cool season of February to April, at which time 

 it goes into a resting condition. Now, if the roots are taken up at 

 this time and carried up to the 6,ooo-foot level, the stimulus of 

 change to the cooler temperature again causes it to awaken and 

 put out a new set of shoots. Exact observations upon this stim- 

 ulative reaction of any plant are possible, and many of the prac- 

 tices of the gardener are the results of long practical experience 

 upon the matter. An interesting set of data have recently been 

 obtained by Dr. B. E. Livingston with respect to the change from 

 the infra-optimum to the optimum with regard to moisture from 

 which it is seen that seeds of Cereus, Fouquieria, Phaseolus and 

 Triticum, germinated when transferred from an air-dry condi- 

 tion to soil containing 15% of water, Impatiens in soil contain- 

 ing 20 to 25%, Raphanus demanded 20%, and Trifolium 25%. 



Gradual changes in the temperature, or in any of the 'other 

 agencies affecting plants, may allow the protoplasm to make such 

 adjustments of the living matter that the cardinal points are 

 much changed and a species may accommodate itself to condi- 

 tions ordinarily unendurable. Experimentation in this phase 

 of the subject has been carried on most with bacteria and the 

 simpler fungi, and it has been found that these organisms are 

 capable of making such slow changes as to be able to undergo 

 temperatures, comparatively very low and very high. The facil- 

 ity with which these organisms may be handled has also led to 

 the result that they have been found to accommodate themselves 

 to very great changes in the composition of the nutrient medium, 

 and to endure the presence of poisonous substances, the concen- 

 tration of which was increased very gradually. 



In all such cases the power of endurance of the plant to an 

 excessive or defective action of any one force is very much modi- 

 fied by the presence of or action of others. Thus, in the matter 

 of the seeds, the endurance to extremes of temperatures is seen 

 to depend directly upon the amount of moisture present. 



Again the time element or the rapidity with which the in- 



