ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
615 
but chrom-acetic acid (0*7 parts chromic acid and 0-3 parts glacial 
acetic acid, in 100 parts water). 
For these “ attractive spheres,” which have the property of inciting 
and directing the binary division of nuclei, M. P. Van Tieghem* pro- 
poses the term “directing leucites” or tinoleucites. 
Nature of Callus.f — Mr. S. Le M. Moore has investigated the 
chemical nature of the stoppers of callus in the sieve-tubes of the 
vegetable marrow and of Ballia callitricha. The following is a summary 
of the chief results. 
The callus of the vegetable marrow gives all the three chief proteid 
reactions ; it is also dissolved by a peptonizing fluid, and is therefore a 
typical proteid. The callus cannot be pressed from the sieve, both 
because it is a proteid, and because, when it undergoes digestion, the 
sieve-plate is “cleared,” and is then left in its pristine condition. The 
stoppers of Ballia give all three proteid reactions, but are not attacked 
by a peptonizing fluid ; they stain in the same way as does callus, except 
that they take a rich brown with iodine alone, and are untouched by 
anilin-blue. The stoppers react altogether differently from the wall of 
the cell-tubes, and to a very large extent similarly to the cell-proto- 
plasm. 
The callus of the vegetable marrow has many of the characters of the 
coagulated proteids, and should probably be classified with them ; the 
substance of the stoppers of Ballia most closely resembles lardacein. 
The function of the callus, in both cases, is to moderate the flow of 
proteids, and direct it so that all the growing points shall receive their 
due amount of the necessary food-material. Many of the phenomena 
presented by the dissolution and renewal of the masses of callus on 
sieve-plates call to mind the action of ferments. 
C 2) Other Cell-contents (including- Secretions). 
Aleurone-grains in Papilionaceae.J: — The following is a resume of 
M. E. Belzung’s researches on the above subject (1) The aleurone- 
grains of LeguminosaB arise at the periphery of the cells ; they are 
small and insoluble in water, and are formed of legumin. (2) Their 
deposition begins when the cell-sap is sufficiently concentrated, and the 
proportion of free acid large enough to cause the precipitation of the 
albuminoid principle. (3) The aleurone-grains enlarge rapidly, and 
then, in virtue of their osmotic property, vacuoles arise. (4) The 
mature aleurone-grain consists of a regular or irregular network con- 
taining in its meshes a sap rich in dissolved albuminoids. A circular 
wall borders a large central aquiferous vacuole. Both network and 
circular wall are insoluble in water. (5) In the species examined the 
aleurone-grains contain no inclosed substances. (6) When the grain 
is completely mature, an albuminoid principle, soluble in water, and 
precipitated by heat or by certain acids, more or less completely 
fills the vacuoles. (7) In the presence of water, and with a tempera- 
* Journ. de Bot. (Morot), v. (1891) pp. 101-2. 
t Journ. Linn. Soc. (Bot.), xxvii. (1891) pp. 501-26 (1 pi.), 
j Journ. de Bot. (Morot), v. (1891) pp. 85-93, 109-16 (14 fi<^s.). * 
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