Varietäten, Descendenz, Hybriden. — Physiologie. 579 



remarkable, group has escaped nolice; that the entire series is one 

 series of naturally related terms; and that the explanation of their 

 real relationship is, ihat they are hybrids between the two species 

 mentioned. Seven recognisably different types are described. The 

 two parent-species are markedly contrasted in most of their mor- 

 phological characters, in their habit ot" growth, and in being mem- 

 bers of two different plant-associations and consequently in their 

 habitats; but crosspollination is possible, because the racemes of 

 both are of the same pattern (elongated and secund). As the two 

 species belong to different plant-associations, the conditions favouring 

 cross-pollination arise only at or close to the boundary between 

 them, while circumstances prevent the hybrids from spreading 

 laterally. Consequently they are usually found in Company with one 

 or other, or both the parent-forms. They have no "specific" charac- 

 ters; being of mixed origin, their characters are inherited, or they 

 are blends or mixtures of the corresponding characters of the parent- 

 forms. As the first Australian, Proteaceous, wild hybrids to be 

 recorded, they are very interesting; also from the way in which a 

 workable (vegetative) balance has been arrived at out of a remarkable 

 assemblage of divergent characteristics. But, in other respects, they 

 are almost failures, little more than botanical curiosities. The}" are 

 not infertile, but they rarely reproduce themselves, because, from 

 the stringent conditions under which they are produced, they are 

 brought into unfavourable competition with the parent-forms for the 

 friendly Services of the birds, upon which their poUination is depen- 

 dent. They are either overlooked, or] if visited, they are likely to 

 be crossed with pollen from one of the parent-forms. 



Author's abstract. 



Baker, S. M., Quantitative Experiments on the Effect of 

 Formaldehyde on Living Plant s. (Ann. Bot. XXVII. p. 

 411—442. 2 pl. 4 textfig. 1913.) 



The authoress describes experiments in which seeds were grown 

 in an atmosphere containing known quantities of formaldehj^de 

 vapour in light and darkness. A comparison of the change in dry 

 weight with that of control cultures with and without COo showed 

 that formaldehyde could be used for the synthesis of food materials 

 to some extent in light; the gain in dry weight Vi^as about half the 

 loss due to respiration, and an increase in the percentage of for- 

 maldehyde in the air did not produce a corresponding increase in 

 dry weight after a certain concentration; an excess of formaldeh3^de 

 w^as toxic. In the dark formaldeh3^de was not assimilated, but ap- 

 peared to stimulate respiration; its toxic effect was more marked 

 than in light. Acetic aldehyde could not be taken up by the plants, 

 hence formaldehyde is not assimilated in light merely by virtue of 

 the aldehyde group. 



The results were capable of two interpretations : 1) formalde- 

 hyde is a Step in respiration and converled by the plant into COg 

 before it can be assimilated, or 2) it is the first step in photosyn- 

 thesis and its further elaboration by the tissues requires light 

 energy. To decide between these two possibilities, quantitative ex- 

 periments w^ere made in which the change in dry weight of the 

 cultures could be directly compared with the CO2 evolved during 

 respiration; it was found that this ratio agreed closely with that 

 calculated for the complete oxidation of a carbohydrate. When for- 

 maldehyde was passed over the cultures in the dark, there was no 



