No. 494] 



PARASITIC PLANTS 



107 



belief in which was formerly universally held. But by 

 those who have given due consideration to paleontolog- 

 ical facts with regard to the evidently sudden introduc- 

 tion at various stages of geological time, not merely of 

 species, but orders and classes of animals and plants; 1 

 to the great array of facts presented by Professor Hugo 

 DeVries in support of his mutation theory; 2 to the cases 

 of aggregate mutation of Lyeopersieuni which I have 

 published from time to time as results of my personal 

 observations f and to like cases of aggregate mutation of 

 Gossypium which have been observed by Dr. 0. F. Cook, 4 

 the proposition that the different forms of phenogamous 

 parasitism have been introduced separately and suddenly 

 will not be hastily rejected. When the attention of one 

 who holds the former of the two views referred to is called 

 to the cases of evidently sudden introduction of animal 

 and vegetable forms during geological time he usually 

 replies by deploring the imperfection of the geological 

 record, although he constantly depends upon it in the 

 multitude of cases in which phylogenetic continuity is 

 evident. And yet, there is no break in the geological 

 record, which is more abrupt and differential than is that 

 which exists between the distinguishing characters of the 

 phenogamous parasites and the normal characters of 

 every other phenogam now living contemporaneously 

 with them. 



Briefly reviewing the foregoing subject, we find as fol- 

 lows: (1) The parasites which have been discussed are 



tution for 1901, pp. 631-640; Bulletin Torrey Botanical Club, New York, 

 Vol. 29, pp. 511-522; Album der Naatur, Haarlem, April, 1903. pp. 231- 

 238; Natur and Schule, Berlin and Leipzig, III Band, pp. 248-253; and 

 Science, New York, Vol. XXII, n. s., pp. 105-113. 

 2 Die Mutationstheorie, Leipzig, 1901. 



'Science, n. s., Vol. XIV, pp. 841-844; ibid., Vol. XVII, pp. 76-78. 

 New York Independent, Oct. 16, 1902; Bull. Torn,/ Hot. Club, Vol. 29. pp. 

 511-522; The Popular Science Monthly, Vol. LXV1I, June, 1905, pp. 

 151-161. 



