ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 777 



tissue which gives off water, the spongy parenchyma of the leaf ; in 

 the other parts of the plant this system is accompanied by the paren- 

 chyma of the wood and medullary rays, which latter convey to the 

 cortex the water required by it ; while in the stem the whole conduct- 

 ing apparatus is also enveloped by cambium. 



Measurement of Transpiration.* — Under the name Potetometer 

 J. W. Moll describes an instrument invented by him for the purpose 

 of exactly measuring the quantity of water given off, in any space of 

 time, by the foliage of plants. 



Exhalation of Ozone by Flowering Plants.f — A series of ex- 

 periments conducted by Dr. J. M. Anders go far to prove that flower- 

 ing plants, especially odoriferous ones, give off ozone under the 

 influence of sunshine. Schonbein papers suspended in glass cases 

 with flowering plants showed under favourable conditions marked 

 blue shades, and though Dr. Anders does not wish to say dogmati- 

 cally that all the changes seen in the test-papers were produced by 

 ozone, he considers it incontestable that this substance was the chief 

 agent in their production. 



With regard to the probable mode of its production, Dr. Anders 

 concludes that " during the formation of the seeds there is a rapid 

 metastasis of phosphorites, in the form of phosphoric acid, and the 

 phosphates to that organ of the plant, and it may be reasonably 

 supposed that in the chemico-vital changes going on in the ovules, 

 phosphorus is liberated and acted upon by the moisture which the 

 leaves and petals are so actively transpiring." Under these circum- 

 stances it not improbably follows that those flowers which produce 

 the most seed are the largest generators of ozone, so that the sunflower 

 may have other than aesthetic claims to our admiration. 



Acids in the Cell-Sap. :|: — G. Kraus has examined the relative 

 proportion of acid in different plants, in different parts of the same 

 plant, and in the same part at different times of the day. As a rule, 

 in most woody and herbaceous plants, the leaves contain the largest, 

 the root the smallest quantity of free acid, though there are exceptions 

 to the rule. In the stem the acidity increases from above downwards, 

 or, in other words, increases absolutely with age. He regards the 

 acids as not mere products of excretion in metastasis, but as playing 

 an important part in the processes of life. In geotropic curvatures 

 the amount of free acid is both relatively and absolutely less on 

 the convex side. 



The formation of acid is, as a general rule, hindered by light. 

 As regards periodicity, the maximum of free acid is found in the 

 early morning ; the amount then decreases steadily till the evening, 

 when it reaches its minimum, increasing again gradually during the 

 night. 



* Arch. N^erl. Sci. Exact, et Nat., xviii. (1883) pp. 469-78 (1 pi.). 



t Ainer. Natural., xviii. (1884) pp. 337-44, 470-7. Cf. Engl. Mech., xxxix. 

 (1884) pp. 313-4. 



X Abh. Nttturf. Gcsell. Hulle, xvi. (1884). See Bot. Centralbl., xviii. (1884) 

 p. 100. ^ 



«tr. 2.— Vol. IV. 3 1' 



