ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 829 



and may be divided into Osteosclereids (bone-cells of HaJcea, &c.), 

 Astrosclereids (opbiure-cells of Jonsson), and Brachysclereids (stone- 

 cells). Except in actual reserve-receptacles, as in seeds, the thickening 

 of the wall is never effected by the storing-up of reserve-cellulose, 



Sclereids are often employed in constructions for producing radial 

 pressure, as the osteosclereids of the Proteaceae, Restiacese, and Thea, 

 and the brachysclereids in the palisade-layer of the testa of seeds. 

 The mechanical contrivances in the bark of dicotyledonous trees are 

 very various ; and the sclereids here often perform a secondary func- 

 tion in protecting the sieve-structures. The " mixed ring " of Quercus, 

 Cinnamomum, Betula, &o., is produced by thin- or thick-walled ele- 

 ments of the cortex becoming intercalated in cavities formed during 

 the early years in the mechanical ring of the primary group of 

 sclereids. The author is unable to explain the function of isolated 

 sclereids or groups of them not connected with bast-cells. In the 

 fruit of the Pomacefe they may be the remains of walls previously 

 continuous, though this will not explain the isolated clusters of stone- 

 cells in older cortex, and the isolated sclereids in the pith of many 

 plants. 



Structure and Function of the Aril in certain Leguminosse.* — 

 Herr E. Bachmann describes the appendage to the seeds known as 

 the aril in Sarothnmnus scoparius and some other Leguminosfe. Its 

 purpose appears to be to cause in the ripe seed a detachment from 

 tlie fimicle, by means of a very large intercellular cavity, and thus to 

 promote the dissemination of the seeds. A similar purpose is served 

 by a totally different structure in the aril of species of Vicia and 

 Lathyrus ; the separation being caused here by a difference of tension 

 between the cells of the aril and those of the seed itself. 



Leaves of Statice monopetala.f — Dr- M. Woronin describes the 

 structure of the leaves of this plant, in which the most noteworthy 

 points are the following : — Among the otherwise very regular layers 

 of palisade-cells immediately beneath the epidermis of the upper and 

 under surfaces, are large much-branched sclerenchymatous cells, 

 containing a colourless finely granular protoplasm, and sometimes a 

 distinct nucleus. The leaves disj)lay a strong calcareous inci'ustation 

 partly in the form of a thick and regular layer, partly in the form of 

 separate scales of roundish outline, which, when violently removed, 

 reveal beneath them remarkable glands consisting always of eight 

 cells, by which the calcium carbonate appears to bo separated. 



Absorbing Organs of Albuminous Seeds- J— Dr. M. Eboling has 

 investigated the process by which, in germinating seeds which have 

 their food-material stored up in cndos[)erm, the embryo obtains this 

 food-material from the embryo. He finds that the various modes may 

 be classified under the following types : — 



In Cycadca) and Monocotyledons the cotyledons remain perma- 

 nently in the seed, and are destined for no purpose except the absorp- 



• Ikr. DcutfK-h. Bot. Gesell., iii. (188.')) pp. 25-9 (1 pi.), 

 t bot. Ztg. xliii. (188.5) pp. 177-85 (1 pi.). 

 : Flora, Ixviii. (188.5) pp. 179-202 (1 pi.). 



