186 SUMMARY OF CURRENT RESEARCHES RELATING TO 



BOTANY. 



GENERAL, 



Including the Anatomy and Physiology of Seed Plants. 



Cytology, 

 including 1 Cell-Contents. 



Specific Gravity of Cell-sap.* — Gustav v. "Walk has studied the 

 specific gravity of the cell-sap in different parts of the plant ; his 

 observations have extended over a large number of species. The limits 

 of concentration were represented by a specific gravity of 1*099 and 

 1*007. In 34 determinations of the specific gravity of growing shoots 

 (from which leaves and apical bud had been removed) of seven plants, 

 including three species of Rumex, Polygonum cuspidatum, and Sambucus 

 nigra, the numbers varied from 1 * 012 to 1 * 024. The difference between 

 the specific gravity of sap from succulent leaves, and that from ordinary 

 mesophyte foliage was not great. In the former (eight plants, chiefly 

 Crassulacese) it ranged from 1*013 to 1*028, in the latter from 1*015 

 to 1 * 044. This is associated with the fact that succulent leaves store 

 not only water but also matter in solution. In special reserve stores 

 (sixteen specimens) a variation occurred from 1*014 in tubers of Mira- 

 bilis to 1 ' 08 in the rhizome of Cochlearia Armoracia. In fruits (seventeen 

 examples) the lowest concentration was in Cucurbita melanosperma, 1 * 013, 

 the experiment being made with the parenchymatous tissue of a fruit 

 which had been kept through the winter ; the highest result was obtained 

 with berries of Berberis vulgaris, namely 1*073. Kraus had previously 

 recorded a specific gravity of 1*08 in Lonicera tartarica. 



A comparative examination was also made at different times of the 

 day, with transpiring plants. Thus in Rheum officinale at 6 a.m., 3 p.m., 

 and 6 p.m. the numbers were respectively 1*015, 1*018, and 1*015, and 

 with Heracleum pubescens 1*019, 1*034, 1*028. The concentration 

 in the leaves in summer was less than that in autumn : thus in Sambucus 

 nigra the results were, in June 1*020, in October 1*056. 



Arsenic in Plants and Animals.t — Armand Gautier finds arsenic 

 in a number of alga?, especially seaweeds (species of Fucus). He remarks 

 that the association of arsenic and iodine in seaweeds is paralleled by a 

 similar association in animal organs (hair, skin, thyroid, &c). He also 

 finds arsenic in the boghead of Autun and Australia, which M. Eenault 

 has shown to contain spores of fresh-water algas. The bacteria of sulphur 

 springs were also found to contain both arsenic and iodine, and arsenic 

 was isolated from the plankton of sea-water. The source of the arsenic 

 which is thus shown to be assimilated by plant and animal organisms is 

 presumably the sediment derived from the primitive rocks. The author 

 found that arsenic always accompanies iodine, nitrogen, and phosphorus 

 in these rocks, and thus appears to play a universal part like nitrogen 

 and phosphorus. 



* Zeitschr. f. angew. Mikr., viii. (1902) pp. 141-64. 

 t Comptes Eendus, cxxxv. (1902) pp. 833-8. 



