BOTANICAL INFORMATION. 233 
ready observed, is excellent, and if properly attended to would 
prevent much of that multiplication of petty orders, which 
only tends to confusion. 
In the special case before us, it is remarkable how easy it 
is to distinguish one of the orders nearest allied to Apocyna- 
cee, the Gentianee, without either Grisebach or Alph. de 
Candolle, than whom none could have better investigated the 
matter, having been able to detect a single constant tangible 
character, except the milky juice of the former, and the bitter 
taste of thelatter, a physiological difference which may affect 
colour or other points, which the eye can appreciate, but the 
pen cannot delineate. The relation to Loganiacee will pre- 
sently be adverted to. ; 
Amongst the generic characters hitherto little attended to 
in Apocynacee, considerable assistance has here been derived 
from the modification of the calycine glands and nectarium, 
and the twisting of the corolla, whether from left to right or 
from right to left, which is shown to be often, though not 
always, constant in genera, and nearly so in the tribes. 
The Asclepiadaceæ had been for several years studied by De- 
caisne and some excellent papers were published by him in the 
Annales des Sciences Naturelles for 1838. The nice and com- 
plicated characters furnished by the sexual apparatus in this 
order are well known from the valuable works of Robert 
Brown. The extreme difficulty of ascertaining them in dried 
specimens may be at once experienced by any one who at- 
tempts their determination, who will readily appreciate the 
tedious labour of examining specimens more or less numerous 
of almost eight hundred species (out of near one thousand enu- 
merated), which has been done with the greatest care and 
accuracy on the present occasion by Decaisne. His materials 
were the rich collection in the Museum du Jardin du Roi, at 
Paris, together with the Asclepiadee from De Candolle’s her- 
ium, transmitted to him from Geneva, and some species 
from the herbaria of Benj. Delessert, P. B. Webb, and 
G. Bentham. He had thus at his disposal the most impor- 
tant of the collections above mentioned as made use of by 
De Candolle, and besides valuable authentic ‘specimens of 
