THE OVARY OF A POPPY. 41 
the parts are maintained by the solid parts of the valve situated 
farther away, and above all by the hardened balsam which sur- 
rounds them. A cement absolutely solid does not offer these 
inconveniences. Balsam is only useful to give a soft rock con- 
sistency and a greater hardness, it cannot be employed to agglutinate 
diatoms already in powder. Other cements I have used have 
given me nearly negative results, but I may mention one method 
which seems to possess advantages, viz., the employment as a 
bedding agent of the solid matter deposited by certain incrustating 
waters. The water from these springs is often employed to obtain 
copies of medals, bas-reliefs, &c., and on being left to itself deposits 
a hard matter consisting in great part of carbonate of lime. On 
mixing frustules of diatoms with these mineral waters a hard 
deposit may be obtained, from which it is easy to cut very thin and 
perfectly transparent sections. Further than this, the calcareous 
cement may be easily eliminated by weak acid, thus leaving the 
isolated sections of the diatoms in a state so that they may be 
mounted separately in a medium more favourable to their study. 
It is not absolutely necessary to have recourse to the artificial 
methods of preparation. Many sufficiently hard rocks contain 
diatoms in greater or less quantity. Certain varieties of guano are 
hard and yield very good sections. There is,there for you a virgin 
soil which will furnish quite as much interesting observation as you 
may wish to explore.—Bul/. Soc. Belge de Microscopie, June 3oth, 
1883. 
HE OVARY “Ocak POPPY. 
ay far as the mere preservation of the individual life of any 
particular plant is concerned, the only physiological duties 
required to be performed by the organism are those every-day 
operations connected with its respiration and nutrition; but as it is 
necessary at an earlier or later period of life to make some provision 
for the preservation of the species, a special physiological function 
at this time manifests itself, resulting, under favourable conditions, 
in the production of offspring, which, strongly inheriting the 
structural characteristics, modes of growth, constitutional pecu- 
liarities, and so forth of the parent, carry forward to another 
generation the direct line of specific descent. In the higher plants, 
at all events, this all-important provision is effected by the forma- 
tion of emébryos contained within structures known as the seeds, 
each embryo being the direct outcome of a sexual act ; that is to 
say, it is produced, or rather its developmental growth is initiated 
