280 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



Liliaceae. Bowstring hemp is obtained from the leaves of Sanse- 

 viera. A superior kind of bast is prepared from the leaf-stalks of Tacea 

 pinnatifida. The large leaws of Aframonium are used for thatching. 

 Coarse rope is made from the bark of species of Trema and Celtis. Ficus 

 rokko, E^itada scandefis, Brachystegia appendiculata, Crotalaria retusa, 

 Lannea Barteri, Paidlinia pinjiata, species of Corchorus, Triumfetta, 

 Gewia, and many of the Malvaceae, including Hibiscus, are all sources 

 of valuable fibre. Cotton is also cultivated in Togo. — S. E. W. 



Town Planting-. By A. D. Webster [Gard. Chron. xlv. (1909), 

 pp. 220, 262, 400). — Trees and plants for town planting are dealt 

 with by an experienced town-gardener. He points out that the tree 

 that flourishes in one town may not be found suitable in another. 

 While in London the London Plane is best, in Shefileld the Canadian 

 Poplar takes first place, in Manchester the lime, and in colliery dis- 

 tricts horse-chestnut and sycamore are important trees. Full direc- 

 tions as to methods of planting, fencing and staking, and on the vexed 

 question of the pruning of tow^n-trees, are given. — F. J. C. 



Transpiration and the Ascent of Water in Trees under 

 Australian Conditions. By A. S. Ewart and B. Pvees (Ann. Bot. 

 xxiv. January 1910, pp. 85-105). — The investigations Vv^ere undertaken 

 to determine (1) the rate of transpiration under Australian conditions; 

 (2) the rate of ascent of sap, more especially in Eucalyptus trees ; (3) the 

 length and diameter of the wood-vessels ; (4) the condition of the con- 

 ducting tissue during transpiration; and (5) the maximal and average 

 resistances to flow in functioning stems. An abridged account of the 

 summary given by the authors is as follows : — 



The rate of evaporation for each square metre of leaf-surface from 

 cut branches, whether placed in water or not, is always less than from 

 a plant rooted in the soil under otherwise similar conditions. When the 

 air is hot and dry the evaporation from a free surface of water under- 

 goes an enormous increase, but that from a living plant undergoes a 

 regulatory decrease, and may be only one-sixth as active as the former. 

 Under optimal conditions a rooted plant of Eucalyptus corynocalyx may 

 lose 396 grams of water for each square metre of .transpiring leaf- 

 surface an hour, whereas the maximum rate for Dracaena Draco was 

 17*6 grams. 



Cut trees always absorb water at a less rate than rooted ones 

 evaporate it. The maximum rate of ascent of sap noted was 12'3 

 metres an hour (Eucalyptus viminalis) and 6'5 metres an hour 

 (E. amygdalina), whereas in cut branches of Eucalyptus it rarely 

 exceeded 1 to 2 metres an hour. 



Single vessels may run nearly from end to end of the main trunk in 

 young Eucalyptus and Acacia trees several metres high, but only a very 

 small fraction exceed half the main trunk in length. In the branches 

 the vessels are shorter and narrower. The existence of a rapid trans- 

 piration current appears to favour the development of broad vessels, but 

 not to affect their length. 



