Physiologie. — Palaeontologie. 109 



Peirce, G. J., The possible effect ot cement dust on plants. 

 (Science 2. XXX. p. 652—654. 1909.) 



A consideration of the effect of dust from a cement work which 

 more or less completely covered the foliage of plants for an area 

 extending six miles from the source. The effect of the accumulation 

 of dust on the surface of the leaves is shown to be mainly mecha- 

 nical, — no evidence of a corrosive or poisonous influence being 

 found. Attention is called to the absence of rain in the region (near 

 Concord, Californial after the leaves of deciduous trees have 

 developed, and the action of frequent fogs is shown to assist in the 

 „setting" of the cement dust, rather than to wash it off. It is 

 concluded that the effect of the dust is to interfere with the exchange 

 of gases concerned in respiration and in food manufacture, as well 

 as offering a mechanical hindrance to growth which will lead to 

 distortions more or less serious. Trelease. 



Sampson, A. W. and L. M. Allen. Influence of physical fac- 

 tors on transpiration. (Minn. Bot. Studies. IV. p. 33—39. 1909.) 

 The aim of the authors was to measure transpiration along the 

 following lines : 



1. To determine the individual Variation of the same species 

 grown and tested under the same conditions. 



{a) In the plant house. 



[b) In their natural habitats. 



Variation found to be slight. 



2. To measure individuals of the same species, some of which 

 had developed in the shade and some in the sun. Polydemic forms 

 developed in the sun lose from two to four times as much water as 

 those developed in the shade. 



3. To determine the effect of altitude and pressure in trans- 

 piration. Other things being equal, an increase in altitude stimulates 

 an increased transpiration. This is not due to increased light inten- 

 sity or lower air humidity, but to decreased pressure. 



4. To determine the relation between the internal structure and 

 the transpiration of an amphibious plant and to compare it with the 

 internal structure and transpiration of land plants. The transpiration 

 of Scirpus lacustris, with a large amount of transpiring tissue, four- 

 fifths of the total value of the stem composed of air Chambers, etc., 

 is almost twice as great as that of Heliaiithiis annuus. 



5. To test the effect of som.e of the common acids and alkalies 

 in transpiration. Generally speaking acid Solutions accelerate and 

 alkaline Solutions retard transpiration, and weak Solutions often 

 produce as marked effects as strong ones, 



6. To study the effect of three common soil types and the in- 

 fluence of soil texture. Plants lose more water by transpiration in 

 soils of course texture than when grown in soils of fine texture. Soil 

 texture seems to have nothing to do with the amount of green 

 weight produced. There appears to be a slight tendency for trans- 

 piration to be depressed in the better soils and there is a correlation 

 between transpiration and the green weight at the tops. 



Trelease. 



Arbep, E. A. N., Fossil Plants. (Gowan and Grey Ltd. 75 pp 

 Price 6 d. 1909.) 



Sixty quarter plate photographs of impressions and.anatomy of 



