252 SUMMAKY OF CUBRENT RESEARCHES RELATING TO 



Corpuscula of Gymnosperms.* — J. Goroschankin has investigated 

 tlie structure of these organs, chiefly in the Cycadese, the species 

 examined being Zamia pumila, Geratozamia robusta, Lepidozamia 

 Peroffshyana, Encephalartos villosus, and Cycas revolufa. The cell- 

 wall of the young corpusculum is always thin and quite homogeneous. 

 In flowers (of Geratozamia) about four months old, thin places 

 have made their appearance in it in the form of roundish dots. When 

 the ovules are mature (before fertilization) it is strongly thickened, 

 and furnished with a number of conspicuous pits. The cell-wall is 

 at all ages coloured blue by chloriodide of zinc, and is therefore 

 composed of cellulose. Connected with each pit is a small canal, 

 without any trace of the septum apparent ; and the protoplasm of the 

 corpuscula is distinguished by a number of protuberances equal in 

 length to the canals. 



By treating the fresh endosperm with very dilute sulphuric acid, 

 after the lapse of a day it becomes somewhat softened, and the cor- 

 puscles with their thick cell-walls can be easily removed ; and, on 

 addition of chloriodide of zinc, the pits in the latter can be very well 

 made out. 



Tangential sections in alcoholic preparations of the corpuscula 

 distinctly showed sieve-plates in the pits, by staining with chlor- 

 iodide of zinc, or better with hgematoxylin. The sieves were not all 

 alike. In smaller pits they formed a uniform very thin network ; in 

 larger pits, besides the network, a coarser striation of the membrane 

 was seen, which, however, passed gradually into the network. The 

 sieve-plates are extremely thin, and require, to make them out, a very 

 careful focusing of Hartnack's objective No. IX. Tinging with 

 hsematoxylin under very high powers shows that these plates are 

 actually peiforated. This can also be seen in longitudinal sections 

 of fresh ovules treated with strong sulphuric acid, and then with 

 iodine or eosin. The sulphuric acid causes a strong and rapid 

 swelling of the cell-wall of the corpuscula, and a rupture of the 

 threads of protoplasm that pass into the canals, the broken ends of 

 which may be readily made out after treatment with iodine. 



These observations on the Cycadese prove, therefore, that the cell- 

 wall of the corpuscula consists of cellulose; and it appears to be 

 thickened only on that side which faces the protoplasm of the 

 corpuscle. It contains a large number of pits, furnished with true 

 sieve-plates, through which the protoplasm of the cells of the adjacent 

 layer of endosperm is in open communication with the protoplasm of 

 the corpusculum. 



Similar sieve-plates were observed in the cell-wall of the cor- 

 puscles of a number of Coniferse belonging to the Abietineae and 

 TaxinesB ; but in the Cupressineas examined no trace of these pits 

 could be detected. 



Comparative Structure of the Aerial and Subterraneous Stem 

 of Dicotyledons.l — J. Constantin has made a comparative study of 

 the stem above and below ground in a large number of dicotyledonous 



* Bot. Ztg., xli. (1883) pp. 825-31 (1 pi.). 



t Ann. Sci. Nat. (Bot.), xvi. (1883) pp. 5-176 (8 pis.). 



