NOTES AND ABSTRACTS. 



641 



Measurement can be made of trees that are located in the heart of 

 the city, in the beginning of the residential portion, and later in the sub- 

 urbs. By such a system of comparison the extent of smoke injury can 

 be obtained long before it can be detected by general examination. 



The method of measurement adopted consists in placing on the 

 upper surface of a leaf, under protection from the air, a filter paper 

 which has been dipped in a 3 per cent, solution of chloride and dried, 

 and noting the time it takes to change from blue to pink. A similar 

 paper is put on the under surface of the leaf, and in this way a 

 quantitative method of comparative transpiration among different 

 plants is obtained. — A. P. 



Smut-fungi, Biology of the. By A. W. Bartlett {New Phyt. 

 vol. xii. Nos. 9-10, pp. 358-361). — The author gives a useful summary 

 of various recent pubHcations on this important group of parasitic 

 fungi, formerly called Ustilagineae, but now placed in a special class — - 

 Hemibasidii — coming just below the Basidiomycetes proper. Apart 

 from the cytological results discussed, the most important part of this 

 note is the summary given of Brefeld's recent work on the biology of 

 the Smut-fungi. These fungi are apparently able to penetrate only 

 into the very young tissues of the host-plant, and when the tissues 

 have reached maturity they are quite inaccessible to the entrance of 

 the parasite. The parts of the plant through which infection can take 

 place are (i) the seedling in a very early stage of development, (2) the 

 young pistil of the flower, (3) all the young growing-points of roots, 

 stems, leaves, flowers, &c. In the first instance infection is probably 

 brought about by the sporidia produced by the resting-spores (chlamy- 

 dospores), which germinate on the soil where they have fallen. In the 

 second, the chlamydospores are probably conveyed by insects or the 

 wind from an infected flower to the pistil of a healthy one, the fungus 

 entering the ovule and the mycelium remaining in the seed during its 

 resting period, renewing its growth only when the seed germinates and 

 then finding its way into the growing-point of the stem ; hence 

 a considerable period may intervene, as also in the first case, between 

 infection and the development of the chlamydospores in the flowers, 

 leaves, or other parts of a plant, and throughout this period (which may 

 last several months) the mycelium in the growing apex of the stem 

 keeps pace in its growth with the growth of the plant without betraying 

 the smallest signs of its presence. In most of the Hemibasidii the 

 chlamydospores are developed in some part of the flower of the host, 

 particularly the ovary, but often in the stamens as well — sometimes 

 exclusively in the latter ; but some species produce these spores in the 

 tissues of the leaves or stem. These spores are well adapted to with- 

 stand unfavourable external conditions ; they often germinate only at 

 the end of a long resting period, and in some species were found to 

 retain their viabiHty for at least ten years. The perennation of the 

 mycelium in the tissues of the host-plant presents some interesting 

 features. This perennation takes place chiefly in the underground 



