440 SUMMARY OF CURRENT RESEARCHES RELATING TO 



The theory now proposed by de Vries, and supported by Moll, is 

 that the production of new species is not due to the gradual accentuation 

 during hundreds or thousands of years, of differences which have sprung 

 up in the form of continuous variations, but is due to the operation of 

 the law of mutation, i.e. to the fixing by heredity of differences which 

 have sprung suddenly into existence. These differ from the continuous 

 variations, not only in their specific characters (sie sind da oder sie sind 

 nicht da), but also in their not disappearing by reversion to the parent 

 type. The new species are distinguished from their parent-forms, not 

 by one character only but by several, and are usually represented by a 

 large number of individuals appearing at the same time. The theoretical 

 conclusion is suggested that this is the history of the formaticn not only 

 of new species, but of all the higher groups also. 



Development of Heat by Plants.* — A series of experiments on dif- 

 ferent plants, carried out by Sig. N. Passerini, showed that the organs 

 of plants exposed to the sun attain a temperature considerably higher 

 than that of the atmosphere ; while those not exposed to the direct rays 

 exhibit usually during the warmer part of the day, a temperature 

 sensibly lower than that of the surrounding air ; the greatest difference 

 observed in the former case was 17° -2 C. The side of fruits exposed to 

 the sun absorbs the greatest amount of heat, hence assumes the deepest 

 colour, and forms the largest amount of sugar. Fruits situated low down 

 nearest the ground absorb most heat, since they receive that reflected 

 from the soil as well as the direct rays. A portion of the heat absorbed 

 directly from the rays of the sun is dispersed by radiation when the 

 calorific rays cease to impinge on the plant ; but the increase of potential 

 energy does not proceed exclusively from the purely luminous rays. 



Influence of the Electric Current on the Resistance of Vegetable 

 Tissues to Conduction. -j- — T. Wjasemsky has followed out the observa- 

 tions of Burdon Sanderson en the electromotive properties of the leaves 

 of Bionsea. He is led to believe that the diminution in the resistance 

 offered by the tissues of the leaf caused by the current is due to the 

 ■conveyance into the tissues of water from the moist electrodes. 



Effect of Hydrocyanic Acid Gas on Seeds.}— From experiments made 

 chiefly on the grains of cereals, C. 0. Townsend has ascertained that dry 

 seeds may be fumigated with the usual strength of hydrocyanic acid gas 

 for the length of time required for the destruction of animal life without 

 in any degree interfering with the germinating power of the seeds, and 

 without rendering them injurious as food. Moist seeds are, on the other 

 hand, much more sensitive to the influence of hydrocyanic acid gas than 

 •dry seeds. 



B. CRYPTOGAMIA. 



Relation of the Zoospore to the Spermatozoid. § — Prof. P. A. Dan- 

 geard compares the modes of reproduction in the lower forms of vegetable 

 life with those in Pohjtoma uvella, the lowest animal organism which 



* Nuov. Giorn. Bot. Ital., viii. (1901) pp. 64-74. 



t Physiol. Russe, ii. (1900) pp. S1-10G (3 figs.) (German). 



X Bot. Gazette, xxxi. (1901) pp. 241-G4 (6 figs.). 



§ Comptes Reudus, exxxii. (1901) pp. S59-G1. 



