210 Miscellaneous. 



I regret that I have not yet been able to verify the parasitic na- 

 ture upon other species than those which occur in our fields. I 

 propose however to examine whether what I have observed in the 

 plants of this neighbourhood will occur or not in analogous plants, 

 or whether this phenomenon is so modified in them as to afford an 

 explanation of the anomalies of structure I am about to point out. 



In a memoir* presented to the Academy, M. Duchartre described 

 in a parasitic plant, Lathreza clandestina, a peculiar ligneous structure, 

 the most prominent character of which is the absence of medullary 

 rays : on the other hand, M. Elie Brogniart in noticing this fact in 

 his report on this paper wished to ascertain whether it did not occur 

 in other plants belonging to the same class as the Clandestine, and 

 he found it in Melampyrum : nevertheless in pointing out the anoma- 

 lous structure in these vegetables, MM. Brogniart and Duchartre 

 did not connect it with the fact of parasitism, but merely saw in it a 

 relation of family. However, this peculiar organization appears to 

 me intimately connected with the parasitic nature of the plants, 

 judging from the uniformity of structure and the black colour 

 of the stems of Pedicularis, Castillegia, Cymbaria, Bartsia, Buchnera, 

 which are all destitute, according to my observations, of medullary 

 rays. 



If parasitic plants assume a black tint mixed with blue on drying 

 — if the absence of medullary rays is one of their attributes — and if 

 these characters are connected with a special absorption of the nutri- 

 tive juices, I may observe that these occur without exception in a group 

 of plants which no one has hitherto suspected of being parasites, I 

 mean the Sundews, which are likewise uncultivable. But with re- 

 gard to the species of Drosera there is another anomaly far more 

 singular to be investigated, that of a dicotyledonous plant being 

 parasitical upon a moss, if, as I suspect, the Sphagnum is necessary to 

 the nutrition of the Drosera. There still remains to ascertain the 

 relation of causality between these characters of structure and para- 

 sitism. 



With respect to the peculiar coloration of the blackening juices 

 which these parasitical vegetables contain, that is a question which 

 belongs to chemistry. In conclusion, the foregoing observations 

 upon Melampyrum, Odontites and Alectorolophus explain clearly why 

 it is impossible to cultivate these plants, which do not meet in the 

 artificial soil of our gardens with the roots of those vegetables at 

 whose expense they live ; it also throws some light in my opinion 

 upon the fact observed by agriculturists, that the Rhinanthacece exert 

 an injurious effect upon the grasses and Cerealia. — Comptes Rendus, 

 July 12| 1847. 



On the situation of the Olfactory Sense in the terrestrial tribe of the 

 Gasteropodous Mollusca. By Joseph Leidy, M.D. 

 While no observer of the habits of the terrestrial Gasteropoda* 

 doubts the existence of the sense of smell in them, but, on the con- 



• A translation of this memoir appeared in the ' Annals ' for June 1845. 



