BOOKS AND CURRENT LITERATURE 



A Criterion of Physiological Vigor. — A recent contribution by- 

 Benedict^ presents what appears to be conclusive evidence of pro- 

 gressive senile changes in the leaves of Vitis vulpina and suggests a new 

 criterion by which different plants may be compared with regard to 

 physiological vigor. The paper opens with a comprehensive review of 

 the present status of our knowledge of senility in both animals and 

 plants. This section is followed by a report of the author's own 

 studies, and this is followed, in turn, by a section devoted to theoretical 

 discussion. 



If a leaf is examined by transmitted light (a photographically en- 

 larged print is actually used), it is seen that the organ is composed of 

 anastomosing veins and intervenal masses of tissue, which Benedict 

 terms vein islets. These islets may be counted and their average area 

 in the plane of the leaf may be determined. It is found that leaves of 

 young plants of Vitis vulpina are characterized by the possession of 

 large intervenal areas, while leaves of old plants have much smaller 

 areas. For plants 3 to 5 years old the average area of the vein islets 

 was found to be 0.4941 sq. mm.; for plants 6 to 11 years old, 0.3727 

 sq. mm.; for plants 14 to 25 years old, 0.2969 sq. mm.; for plants 28 

 to 35 years old, 0.2211 sq. mm.; and for plants 50 to 70 years old, 

 0.1638 sq. mm. With increasing age of the plant the decrease in the 

 size of the intervenal areas is first very rapid and then slow, but it 

 still decreases between ages of 60 and 70 years and no evidence is pre- 

 sented to favor the supposition that a constant size is attained with 

 great age, though this might be expected. At any rate, plants much 

 older than 70 years must be studied if a limit of this decrease is to be 

 discovered. Here, then, is a simple means by which the age of this 

 plant may be approximately determined, without cutting the stem. 



Of course the intervenal areas increase in size with the development 

 of the individual leaf, but the range in size is found to be related to the 

 age of the plant. Thus the various stages of leaf development for a vine 

 25 years old showed a range of islet area of from 0.010 to 0.190 sq. mm., 



1 Benedict, H. M., Senile changes in leaves of Vitis vulpina L. and certain 

 other plants. Cornell Univ. Agric. Exp. Sta. Memoirs 7: 281-370, 1915. 



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