596 RECORD OF CURRENT RESEARCHES RELATING TO 



alcoholic solution of tlieir cliloropliyll. A marine alga, Ulva Laduca, 

 sliowecl no precipitate of tannin when treated in the same way ; and 

 the same was the case with a moss, Hypnum triquetrum, examined in the 

 mouth of March. 



Functions of Vessels.* — In a somewhat elaborate article on this 

 subject, J. Bohm gives two reasons for arriving at conclusions in 

 some respects at variance with the views hitherto entertained. 



The dictum dogmatically asserted by Schleiden, that the matnrc ves- 

 sels, and especially the spiral vessels, never contain water, but only air 

 — an assertion made on his authority by most subsequent writers — Bohm 

 maintains, from the result of a series of observations, to be incorrect. 

 The original fluid contents of the cambial vessels are in most jilants 

 partially, in others completely absorbed by the sap-condncting cells, 

 without any corresponding volume of air being given off. When the 

 vessels have become older, they are filled from the adjoining cells 

 either more or less completely with saj) or with air of ordinary 

 tension. In those vessels whose gaseous or fluid contents are subject 

 to less than the ordinary atmospheric pressure, drops of gum or 

 protoj)lasm are given off from the adjoining cells through the bordered 

 pits, the latter being enveloped in cellulose, and developing into the 

 so-called " Tiillen " or " thyllfe." Air-dried branches in which the 

 vessels do not possess thyllae absorb only a small quantity of water. 

 Branches cut ofl" and placed immediately in water in the summer 

 increase considerably in weight, but if laid for any time in dry or 

 damp air before being placed in water, they absorb only so much water 

 as they lose by evaporation. In the first case the vessels immediately 

 absorb water ; in the latter case their open ends become filled with 

 air, and hence less easily permeable to water. 



B. CRYPTOGAMIA. 



Cryptogamia Vascularia. 



Embryology of Vascular Cryptogams, f — Leitgeb contributes a 

 paper on this subject to the ' Proceedings of the Vienna Academy of 

 Sciences,' relating chiefly to the Ehizocarpeas. The following are 

 the principal results arrived at : — 



1. The position of the first partition-wall in the embryo of Marsilea 

 is a definite one, and independent of that of the macrospore and 

 prothalliiun, inasmuch as it in all cases includes more or less exactly 

 the axis of the archegonium ; but it is movable round the latter, and, 

 as soon as the axis of the archegonium deviates from the vertical, 

 assumes such a position that the embryo is divided into two superposed 

 halves. 



2. The embryos of Marsilea and Salvinia resemble in their 

 development those of the Polypodiacefe until the formation of the 

 octants. The organs are developed after the formation of the 

 octants ; up to this time the embryos are thallomes. 



3. The " pedicel " of Salvinia is developed from that half of the 



* ' Bot. Zeit.,' xxxvii. (1879) pp. 225, 2il. 



t ' SB. Akad. Wiss. Wien,' Ixxvii. (1878) p. 222. 



