INVERTEBKATA, CRYPTOGAMIA, MICROSCOPY, ETC. 983 



threads of protoplasm, which may be extended to a greater or less 

 distance, or may be retracted, and resemble in all points those of 

 Dipsacus. The leaves of Silphium are also united into a kind of cup 

 as in Dipsacus, and probably serve both as a reservoir of water to 

 protect them against the attacks of insects and mollusca, and as a trap 

 to catch insects for the sake of the nutriment derived from their bodies. 

 It is suggested that the occurrence of these threads in connection with 

 the leaf-cups in the two genera probably shows a certain relationship 

 between tlie two parts, and the former one probably utilized for the 

 absorption of nitrogenous substances from the water, as supposed by 

 Darwin to be the case. The glands of Silphium differ from those of 

 Dipsacus in their multicellular stalk, unicellular elliptical head, 

 smaller size, and greater numbers. 



Resin-passages in the Coniferae.* — As a sequel to previous 

 investigations of the subject,t T. F. Hanausek has now examined the 

 resin-passages in the cone-scales of Pinus Laricio, Abies pectinata, and 

 A. Larix, with the following results. 



Tlie epithelium of the resin-passages is neither lignified nor 

 suberized, but consists of cellulose only, with the exception of that of 

 Biota and Abies pectinata, which undergoes a transformation resembling 

 suberization. In the cone-scales of conifers there are both schizo- 

 genous and lysigenous resin-receptacles, the former in the bast-fibre- 

 zone, the latter abundantly in the fundamental tissue. The position 

 of the resin-passages appears often to depend on the position and 

 development of the vascular bundles, and to be associated with their 

 formation. 



The author distinguishes four kinds of resin-formation : — (1) The 

 resin may be formed as a true secretion in true secretive organs. (2) 

 It may arise from a deliquescence of the outer walls of particular cells 

 (schizogenous resin-passages). (3) From metamorphosis of the entire 

 cell-wall and cell-contents (lysigenous and pathological resin-pas- 

 sages). (4) By the transformation of certain contents ; this frequently 

 occasioning an increase of the resin formed in the 2nd and 3rd modes. 



In the cones of Finns and Biota, which remain green for so long a 

 time, the resin, which frequently escapes and flows over the outside of 

 tlie scales, must serve as a protection against the attacks of birds ; 

 when the scales become woody and nearly free from resin, the seeds 

 arc already ripe, and no protection is necessary. 



Influence of Light on the Transpiration of Plants.^— The re- 

 sults of the experimental researches of M. 11. Comes a"ree entirely 

 with the facts already obtained on physical principles, and he sums 

 them up in the following projjositions § : — 



1. The emission of aqueous vapour which takes place in plants is 

 subject not only to the action of the physical agents which influence 



* ' JB. N. Oestr. Laiidca-olKTical- u. Ilandelsch. in Krciiis,' xvii. (1880) Seo 

 ' Bot. Cuntrulbl.,' i. (ISSO) p. TTC 



t Sec this Joiiriiiil, miti-, |>. 1 1:!. 



X '(Joinptcs ReiitluH,' xci. (18.S0) p. 335. 



§ Tho dctiiilH of tlie txpcriiiu'iits, tlio nunicrit-al flntii, plutea, &c., will bo 

 published iu ' Atti U. Accad. Liiicui ' (Mem.), vii. (1880). 



