ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 569 



Physiology. 

 Nutrition and Gi'owth. 



Aerial Roots of Aroids.* — K. Linsbauer lias experimented with the 

 iierial roots of Aroids, with special reference to then* growth and geo- 

 tropism. The author finds that usually the nourishing roots have a very- 

 long zone of growth. The compensating roots which develop in con- 

 sequence of the wounding of such roots behave similarly to an ordinary 

 root. The length of the zone of growth of an attaching root is con- 

 siderably less than that of a nourishing root. The relative rate of growth 

 of a nourishing root is less than that of an attaching root. The daily 

 growth of the nourishing and attaching roots is not greater than that of 

 ordinary earth-roots. The typical nourishing roots of the Aroids are 

 generally positively geotropic, but their geotropism is not very marked, 

 for they may retain a horizontal position for days at a time. Many 

 nourishing roots under favourable external conditions are either entirely 

 or periodically ageotropic. Typical attaching roots are usually ageotropic. 

 Nourishing and attaching roots, as long as they are growing, bear stato- 

 liths in the well-marked columella of the root-cap, and this character is 

 independent of their geotropism. 



Hybridisation of Wild Plants.f — D. T. MacDougal records the 

 results of observations of hybridisation among oaks. The author finds 

 that only under very exceptional conditions can the facts of geographical 

 distribution be relied upon to furnish evidence as to the origin of a 

 species or hereditary quality. Synthetisafcion, when successful, gives 

 reliable conclusions as to the composition of a hybrid, but failure to 

 produce a hybrid may be due to reciprocal crossing, or to difference in 

 physiological attributes. While cultural tests of the progeny of a hybrid 

 will furnish no evidence as to origin, if the progeny exhibits alternate 

 inheritance, there will be unmistakable signs of the nature of the original 

 oross. 



CRYPTOGAMS. 



Pteridophyiia. 

 (By a. Gepp, M.A., F.L.S.) 



Terns of Brazil.:}: — H. Christ publishes an account of the pterido- 

 phytes collected in San Paulo by the Brazilian expedition of the Imperial 

 Academy of Science at Vienna. The specimens come from the rain- 

 forests and the open plain, and are mainly hygrophytic, some from the 

 plain being xerophytic. A small number also were obtained from the 

 plateau of Minas Geraes and the Serra d'ltatiaya ; these are decidedly 

 xerophytic. The entu'e collection comprises 304 Filicinea^ and 15 

 Lycopodieae, 23 species being new to science. The author, discussing 

 the question of fern distribution in Brazil, points out that South Brazil 

 and especially the dry highlands of Minas form an important endemic 



* Flora, xcvii. (1907) pp. 267-98 (2 pis.). 



t Bot. Gazette, xliii. (1907) pp. 45-58 (4 figs.). 



t Denkschr. k. Akad. Wiss. Wien, Ixxix. (1906) 53 pp. (9 pis.). 



