916 SOMMARY OF CURRENT RESEARCHES RELATING TO 



Method of Bursting of Sporangia and Pollen-sacs.*— H. Schinz 

 has investigated this subject. He regards the cause of the bursting 

 to be peculiarly thickened " ojjening cells," which effect a bending of 

 the wall of the anther or sporangium from their change of form on 

 drying. This change of form is effected in two different ways: — (1) 

 In Enceplialartos by a strong thickening of the outer wall of all the 

 peripheral cells, by means of a substance full of water, and the con- 

 traction of these parts in the tangential direction on drying ; the 

 anther-wall consists of three layers, the outermost layer causing the 

 expulsion. (2) In all other structures, by a mode of thickening 

 which causes a hinge-like motion of the actual cells ; i. e. an approach 

 of their outer margins next the epidermis on drying, resulting from 

 the inner and side-walls of the cells being strongly thickened, the 

 loss of water on drying affecting to the greatest extent the innermost 

 layers which bound the cell-cavity. Of this latter mode there are 

 three varieties, viz. : — (l) The sporangia of ferns; the wall consists 

 of one layer ; the opening-cells are converted into an annulus. (2) 

 Gymnosperms, except CycadesB ; the wall consists of one layer of 

 scalariform opening-cells, (3) Cycadeae, except EncepJialartos ; the 

 wall consists of three layers; all the epidermal cells thickened after 

 the manner of an annulus. (4) Angiosperms ; the wall consists of 

 three layers ; the endothecium composed of cells thickened in the' 

 hinge-fashion, and alone taking part in the bui'sting. 



Pollen from Funereal Garlands found in an Egyptian Tomb.f — 

 C. F. White figures the pollen-grains and anther of Palaver Bhceas 

 from the funereal garlands found in Egypt in the coffin of the 

 Princess Nzi Khonson of the XXI. Dynasty about 1000 e.g., and 

 compares them with drawings from recent gatherings of the plant. 

 The former appear to be slightly the larger. Mr. White especially 

 calls attention to the readiness with which these ancient specimens 

 absorb water and expand into that subspherical shape so usual 

 with pollen of simple form ; with the peculiarity that the Egyptian 

 assume the three-lobed shape common to many pollens, the furrows 

 becoming deeper than when dry, instead of, as generally happens, 

 being nearly obliterated when placed in water. No indication of the 

 apj)earance of the pollen-tubes could be detected except that at one of 

 the three points at which they would be produced, a small bubble of 

 air was in several cases observed. 



Swelling Properties of Vegetable Cell-membrane.J — F. von 

 Hohnel has tried a series of experiments on the capacity of swelling 

 possessed by different vegetable fibres : — aloe, Phormium tenax, Manila 

 hemp, flax, Boehmeria tenacissima, and hemp. He finds that, under 

 long-continued swelling, fibres may first increase and then decrease 

 in length. A dry membrane artificially compressed in the direction 

 of its length acquires positive optical properties ; it then increases 

 in length under swelling in water and becomes again negative. 



* Schinz, N., ' Unters. ii. d. Mechanismus d. Aufspringens d. Sporangien u. 

 Pollensacke ' (3 pis.) Zurich, 1883. See Bot. Centralbl., xviii, (1884) p. 361. 

 t Journ. Lmn. Soc. Lond. (Bot.) xxi. (1884) p. 251 (1 pi.). 

 X Ber. Deutsch. Bot. Gesell., ii. (1884) pp. 41-51. 



