392 Botany. 
sults required, if the seeds were made to vegetate under parti- 
cular gases, water of the same quality being used in each case. 
Hitherto much difficulty and uncertainty has been experienced 
in constructing hygrometers.—Query, Have any experiments been 
tried to ascertain how far absorbing substances might be used in 
forming them? Might not one be constructed, by exposing a 
given portion of perfectly dried mouldering whin-stone to the 
air for a certain time, and observing the increase of weight ? 
Common brick-dust or sulphuric acid are also well known to be 
equally absorbent, and might be used with success. E.S. 
*,* Experiments similar to some of those recommended by 
our correspondent have been made at different times; but they 
may certainly be varied and extended. Absorbent substances 
have been tried as hygrometers; none however will answer the 
purpose that do not possess also the property of giving off mois- 
ture, in dry weather, within the usual range of atmospheric tem- 
perature. Sulphuric acid therefore, and all substances that have 
a strong tendency to absorb water, but not to part with it, must 
necessarily be excluded from hygrometric substances, in the com- 
mon acceptation of this term. T. 
CYCAS CIRCINALIS. 
In the month of June last year there was exposed for sale in 
the flower-market of Paris, a plant rarely met with in northern 
countries, and which attracted a great deal of notice. It was 
the Cycas of the East Indies (Cycas circinalis), a species of palm 
and an evergreen, the stalk of which rises in its native habitat 
to the height of from three to five metres, and then divides into 
a number of very short branches. It is crowned by a cluster of 
leaves of a beautiful glossy green, which are curled inwards pre- 
viously to their perfect development, but afterwards turned out- 
wards. The collets of the male flowers take sometimes an ap- 
pearance very similar toa large pine-apple. The female flowers 
yield an oval nut of the size of a small orange. The Indians 
eat the almonds of these fruits, and make asort of sago of them 
which they prize greatly. The nuts of the Cycas of Japan (Cy- 
cas revoluta) are particularly valued on this account. The speci- 
men then exhibited in the Parisian market had five stalks very 
straight, and armed with prickles in a manner nearly similar to the 
Eglantine. The Emperor of Austria gave for the fellow of it in 
1814 no less than 5000 francs (2082. 6s. English). 
CACTUS TRIANGULARIS. ; 
Mr. Shrader, of Baltimore, possesses a Cactus triangularis of 
extraordinary beauty, and perhaps the only one in full vegetation ~ 
in the United States of America. On the night of the 27th of 
August 
