AGRICULTURAL BOTANY. 327 



to warrant the taking of the carbon dioxid given off as an index to the germina- 

 tive capacity of the seeds. 



The respiration of the vegetative organs of vascular plants, G. Nicolas 

 (Ann. Set. Nat. Bot., 9. scr., 10 (1909), No: 1-3, pp. 1-113).— An investigation 

 was made of the comparative respiration of the blades of leaves and their 

 petioles and of stems, roots, and other parts of plants that may function as 

 respiratory organs. After reviewing the various theories regarding respira- 

 tion and describing the methods of his experiments, the author gives detailed 

 accounts of his investigations on the normal and intramolecular respiration of 

 different parts of a large number of species of plants. 



The blades of the leaves were found to respire more per unit of weight than 

 the petioles and the petioles more than the stems. The exchange of gases in 

 respiration is largely effected through the epidermis, while the water vapor 

 escapes through the stomata. This was shown by applying layers of vaseline 

 to the lower surfaces of the leaves, thus closing the stomata, when it was 

 found that this prctceduri' reduced transpiration much more than it checked 

 respiration. 



The author also considered the possible relation of the number and nature 

 of the chloroleucites to resipration, the zymase theory of respiration, the rela- 

 tion between respiration and acidity of tissues, etc. 



An extensive bibliography completes the article. 



Influence of physical factors on transpiration, A. W. Sampson and Louise 

 M. Allen (Minn. Bot. Studies, Jf (1909), pt. 1, pp. 33-59, dgms. //) .—Experi- 

 ments were carried on with a large number of plants to determine the individual 

 variation of species ; to measure individuals of the same species, some of which 

 had developed in the shade and some in the sun ; and to determine the effect 

 of altitude and pressure on ti'anspiration, the relation between the internal 

 structure and transpirations and the effect of acids, alkalis, and soil types on 

 transpiration. 



The authors found that the variation in transpiration per unit of surface for 

 a given time was very slight in plants of the same species, whether grown in 

 their natural habitats or in the plant house. 



Of polydemic forms, when measured in their natural habitats, those devel- 

 oped in the sun were found to lose from 2 to 4 times as much water as those 

 developed in the shade. When the two forms are placed in a sunny or shady 

 situation the inequality of their transpiration is about as manifest in the sun 

 as in the shade. 



Other things being equal, an increase in the altitude was found to stimulate 

 an increase in transi)iration, and this was not due to dift'erences in light inten- 

 sity or lessened air humidity but was due to decreased pressure. This con- 

 clusion was checked under controlled conditions, showing that the greatest 

 transpiration takes place where there is the least pressure. 



Generally speaking, acid solutions accelerate and alkaline solutions retard 

 transpiration, but in a few cases extremely weak alkaline solutions were found 

 to increase it. Transpiration is often found to give as marked response to weak 

 solutions as to stronger ones. Plants were found to lose more water through 

 transpiration per unit of surface when grown in soils of coarse texture than when 

 grown in soils of fine texture. This is believed to be due probably to the fact 

 that physiological water is more abundant in coarse soils than in the finer ones. 

 The soil texture appeared to have nothing to do with the amount of green 

 material produced in the experiments. There appeared to be a slight tend- 

 ency for transiiiration to be depressed in the better soils and a correlation was 

 found to exist between transpiration and the green weight of the tops of plants. 



