102 MASSACHUSETTS HORTICULTLRAL SOCIETY. 



During this series of observations the fact that a larger number of 

 abnormalities than common Avere being produced began to force 

 itself on the writer's attention. The most common abnormality 

 was the production of variegated sprouts. Numerous cases of true 

 variegation could be found in almost every grove. Abnormalities 

 in form of leaf were also common, and, rarer, total changes in t^-pe 

 of leaf. Several instances of bud variations on orange, lemon, and 

 pomelo were noticed where the foliage had become trifoliate. 

 Numerous instances were observed where lemon and orange trees 

 produced branches with small leaves and short intemodes, similar 

 to the so-called INIyrtifolia orange. Without attempting here to 

 enumerate all the cases of variation observed, it is sufficient to 

 state that so many variations were observed that the writer was 

 led to conclude that they were stimulated or caused in some direct 

 or indirect way by the shock due to excessive cold. The variations 

 observed were naturally all the so-called bud or clonal variations, 

 but there is every reason to suppose that the forces causing such 

 variation are the same as those causing seedling variation. 



Tower in his extensive researches on "Evolution in Chrysomelid 

 Beetles," recounts a number of experiments where, when the male 

 and female beetles were subjected to extremely hot, dry conditions, 

 accompanied by low atmospheric pressure, during the period when 

 the eggs and sperms were being formed, there were formed in the 

 progeny many abnormal forms or mutations, which behaved in 

 further cultures as distinct races. 



Experiments conducted by Mr. H. B. Frost in the Cornell De- 

 partment of Horticulture indicate that stocks grown in a warm 

 greenhouse show much greater variation and more abnormal and 

 monstrous tA'pes than similar plants grown in greenhouses kept at 

 medium and cool temperatures. All in all, the gradually accu- 

 mulating data seem to indicate that in severe temperatures applied 

 at certain periods in the life of the individual, we may have a means 

 of stimulating greater variation. The evidence as yet, however, 

 is very incomplete. 



Ex-periments are being conducted also in feeding plants with 

 different chemical solutions and out of the mass of evidence now 

 being accumulated it seems probable that some method or methods 

 will be discovered by which we may induce plants to produce 



