590 FOURTH REPORT — 1834. 



On the application of a Vernier to a Scale, not of equal, but 

 of variable parts, and particularly to Wollastons Scale of 

 Chemical Equivalents. By Professor Stevelly. 



The form of this instrument is that of a pair of lazy tongs, 

 consisting of a series of parallelograms, placed in a line, angle 

 to angle, whose diagonals, when the series is drawn closer or 

 pushed further apart, diminish or increase, according to the 

 same law that connects the divisions of the portion of the 

 scale which is to be read off. An adjusting-screw passes along 

 the whole length of the vernier ; ten divisions of which being 

 made by the adjusting-screw to equal eleven on the scale, 

 the vernier is set for marking decimally : the marking-points 

 are formed by thin metallic blades coinciding with the cross 

 diagonals of each parallelogram. 



IV. NATURAL HISTORY, ANATOMY, AND 

 PHYSIOLOGY. 



BOTANY. 



On the 2)lurality and development of Embryos in the Seeds of 

 Coniferce. By Robert Brown, LL.D. 8(c. 



The earliest observations of the author on this subject were 

 made in the summer of 1826, soon after the publication of his 

 remarks on the female flower of Cycadece and Coniferce. He 

 then found that in several Coniferce, namely, Pimis Strobus, 

 Abies excelsa, and the common larch, the plurality of embryos in 

 the impregnated ovulum was equally constant, and their arrange- 

 ment in the albumen as regular as in Cycadece; and similar ob- 

 servations made during the present summer on several other 

 species, especially Pinus sylvestris and P. pinaster, render it 

 highly probable that the same structure exists in the whole 

 family. 



The first change which takes place in the impregnated 

 ovulum of the Coniferce examined, is the production or separa- 

 tion of a solid body within the original nucleus. 



In this inner body, or albumen, several subcylindrical corpus- 

 cula, of a somewhat different colour and consistence from the 

 mass of the albumen, seated near its apex and arranged in a 

 circular series, soon become visible. 



In each of these corpuscula, which are from three to six in 

 number, a single thread or funiculus, consisting of several, 



