E x = lensis, n of my observations on which, I sent 
XVI PREFACE. 
permanent nature to ensure the maturity of the 
parasite: These plants are simply imbedded but 
there is no interchange of structure, unless in the 
case which not unfrequently happens of the sucker 
of one passing into that of an other belonging to 
the same plant.. 
Most of the accounts of the mode in which this para- 
sitism occurs appear to be incorrect, at least 
most of the Indian species, are not confined to union 
by one spot. In these, roots are indefinitely thrown 
out, which contract unions with the stock indifinitely. 
- Deboro Mookh, Feb. 29th, 1836, 
Asclepiadee.—The subject of impregnation in 
this order has been lately cleared up and pushed to | 
an extent certainly unequalled in any other branch 1 
of organic Natural History. Brouginiart claims the I 
honour of having discovered this, but I am inclined to | 
give the whole credit to Dr. Brown, especially when 
we take into consideration one very great error into 
which Mr. Brougniart has fallen, I allude to his state- 
ment of the dehiscence of the pollinias and conse- 
quent fecundation occurring in the cells of the anther. 
Mr. Brown has published his observations in the Linn. 
Soc. Transactions, in which however he had traced the 
tubes to, but not into, the ovula of Calatropis gigan- 
tia—and about the same time traced them to the 
placenta in Hoya viridiflora. Mr. Brown was the first 
who traced them into the ovula. He tells me that 
Treviranus had likewise succeeded. Wight has also 
: ded in pairs gigantia. I have traced them 
to the same point i in Dischidia Rafllesiana and bengha- 
