250 On the Parasitism of Comandra Umbellata. 
increased only 124 per cent. If m=-85, the increase of power 
is 46 per cent., while that of the volume of air is only 28 percent. 
It is, nevertheless, still a question to be settled experimentally, to 
what extent the volume of air can be increased, without exceed- 
ing the power of the furnaces. But at any rate we are justi- 
fied at present in saying, that there is no good reason, as Be for 
despairing of the success of this ingenious invention 
Univ. of Alabama, June 1, 1853. 
Art. XXVII.—Note on the Parasitism of Comandra umbellata, 
Nutt.; by Asa Gray. 
So long ago as the year 1847; Mr. William Mitten, an Eng- 
lish botanist, communicated to’ Hooker’s London sail of 
Botany, (vol. vi. p. 146, plate 4,) a brief article, on the economy 
of the roots of Thesium linophyllum ; in which he shows that 
the roots of this plant are parasitic ; the ramifications of the root 
forming attachments, by means of suckers, with the roots of ad- 
jacent plants of various species. he same parasitism probably 
occurs in other species of T’hesium, if not in the genus generally. 
But I am not aware that the fact has been confirmed on, the con- 
tinental species, which are somewhat numerous, although atten- 
tion has been called to the subject by the reprint of Mr. “Mitten’s 
article in the Annales des Sciences Naturelles (in the volume 
which bears the nominal date of 1847,) and an interesting exten- 
sion was at once given to the discovery by M. Decaisne, who de- 
tected a similar parasitic attachment of the rootlets of Melantpy- 
rum pedicularis, and other rhinanthaceous plants long known to 
be uncultivable. 
In the Botanical 'fext-Book, I had called attention to the re- 
lated genus Comandra, which replaces Thesium in this country, 
as likely to exhibit the same parasitic economy, but, pressed by 
other occupations, =e neglected to make the examination my- 
self, nor had I any notice of the observation having been made by 
others, although ecg umbellata is everywhere a common 
plant in the United States. 
The discovery, however, has now been made by my esteemed 
correspondent, Mr. Jacob Stauffer, of Mount Joy, Lancaster 
County, Pennsylvania. He has recently sent me fresh specimens 
of Comandra umbellata, with its elongated and woody subter- 
ranean stems, giving off numerous roots, the branches of which 
are often expanded at their tips, into a small tubercle or sucker, 
which is implanted by its disk-like surface upon the bark of a 
jacent roots, principally. of shrubs. The foster-plants, in the 
specimens communicated, are Blueberries and Huckleberries, 
