NOTES AND ABSTRACTS. 



829 



petiolare the roots are so dense and abundant that they grow out of the 

 soil and creep downwards along the outside of the pot to the sand below. 

 A figure of this is given. Leaves of Ginkgo, which Lindemuth was 

 unable to root, rooted freely, but never formed young plants, the leaves 

 gradually yellowing and dying off.— W. C. W. 



Lettuce and Tobacco Growing". By W. E. Embry (U.S.A. Exp. 

 Stn. Florida, Fanners' Ins. Bull., 1904). — Sheds are constructed, at a 

 cost of $250 per acre, in which to grow Tobacco, and are found admirable 

 in Florida for cultivating Lettuce and other vegetables. The coverings 

 of the sheds are made of slats 1 inch by g inch by 50 inches, interwoven 

 with No. 22 wire, 650,000 being required to the acre, the slats being 



1 inch apart. The sheds are supported by posts, 11 feet long, having 



2 feet in the ground. — F. J. C. 



Lichen Anatomy (Usnea). By Fritz Schult (Dortmund) (Beih. 

 Bot. Cent, xviii. Abt. ii. pp. 1-22 ; 3 tables and 8 text figures). — Gives a 

 very thorough description of the anatomy of this genus. The spiral 

 course of the cells forming both the outer and the inner rind is specially 

 interesting. The author discovered constantly ascogenous hyptue from 

 which the asci clearly originated, but never found either trichcgynes or 

 spermatia, and he holds that these ascogenous hyplue are produced by 

 vegetative growth of the aeration tissue. The paraphyses seem to be 

 clearly traced from the hypothecium. 



Barbatin acid, traced by solution of potassium bicarbonate, was found 

 in U. ceratina and U. longissima only. Beautiful crystals are formed of 

 this. Usnic acid is found only in some species, whilst calcium oxalate 

 occurs in all the species examined. — G. F. S.-E. 



Light, The Attraction of Organisms to. By Em. Radl {Flora, 



xciii. 1904, pp. 167-178). — The author, dissatisfied with current views 

 on phototropism, relates experiments tending to show that a seedling hung 

 by a silk filament like a magnet needle sets towards the light, and ascribes 

 the result to the direct impulse of the light rays. [Probably a quartz 

 filament would have given more trustworthy results.] — M. H. 



Lightning*, Trees stag-headed by. By K. von Tubeuf (Nat. Zeit. 

 Land-Forst. i. pp. 1-9, 309-315, 367-372, 413-461 ; ii. pp. 6-62, 109- 

 112 ; 54 figs, and 17 plates ; 1903-1904).— The first part of this research 

 has already been referred to (see Joukn. B.H.S. xviii. p. 295). The later 

 parts give details of the observations, and the numerous illustrations 

 show that great care has been taken. The author establishes his view 

 that one cause of stag-headedness of Conifers (Spruce, Larch, Pine, and 

 Silver Fir) may be lightning. In most of the cases the trees were struck 

 during the winter 1902-3, and apparently by continuous small discharges, 

 because the damage differs distinctly from the well-known injuries caused 

 by forked lightning. In every case the tree stood higher than its neigh- 

 bours. The result is that a portion of the crown is completely killed, and 

 death, accompanied by discoloration of the bast region, extends some 

 distance down the living part of the tree. This discoloration is shown 

 by several coloured plates, and is sufficient to diagnose the damage and 



