PHYLLOCACTUS x Census. 



97 



of parentage is reversed, and we are told that the hybrid was raised on 

 P. crenatus. In certain botanical lists the faulty genealogy in the 

 heading has been copied, and whatever effort we may now make to 

 correct it, it will be impossible to catch up this mistake.* This shows 

 the importance of following mother-kin in genealogies of plants. 

 Maternity, as Draper said, is a matter of fact, paternity of specula- 

 tion ; and, although it is true that this speculation may be avoided, 

 the proof that it has been avoided is rarely forthcoming. 



(3) P. x Thomasianus f is listed by the late Dr. Schumann as a 

 hybrid of the same section as P. X Wrayi. It resembles the latter in 

 three respects : (1) the plant is quite unarmed, (2) the tube is distinctly 

 curved, and (3) the flowers are white with yellow to brown sepals. 

 These three characters appear as constants in all the ascertained 

 hybrids of P. crenatus and C. grandiflorus . But P. x Thomasianus 

 differs from P. X Wrayi in having a 14-partite yellow stigma and 

 also (perhaps) in the great number of its yellow stamens. Moreover, 

 in P. x Wrayi the tube is longer and the sepals more intensely coloured. 



I have found no evidence that from some known hybridization of 

 Cacti diverse hybrids may result, even if we include reversed genders. 

 But, if we accept the allegations which are made, then not only are 

 the diverse hybrids Wrayi and Cooperi of the same parentage, but 

 we must believe that no fewer than nine presumably distinct hybrids 

 have sprung from the intercrossing of C. grandiflorus and C. 

 speciosissimus.X 



I know of but one instance in which diverse hybrids have sprung 

 from one interspecific cross, and this did not occur among the Cacta- 

 ceae. § Hence we must await evidence before accepting statements 

 which contradict our general experience of interspecific hybridiza- 

 tions. 



Comparison between P. Wrayi and P. Cooperi. 



There are at least seven characters in which conspicuous differences 

 are noticeable. P. x Wrayi is taller, quite unarmed, and carries its 

 flowers near the top of the sterns ; X Cooperi is dwarfer, armed, 

 and carries many of its flowers very near the ground level. The tube 

 in x Wrayi is 5-angled and bears large scales ; in x Cooperi the 

 tube is nearly smooth, not angulate, and bears small scales. The 

 green stamens of x Wrayi give the flower a greenish tinge not to 

 be seen in x Cooperi, and the fragrance of the flowers is quite 

 different. 



* It is possible that Wrayi and Cooperi may be the product of the same parents 

 but with gender reversed. 



f Bluhende Kakteen, PI. 41 ; Schumann, Monograph, V. 1895. 

 % Conference on Genetics, London, 1906, p. 407. 

 § Ibid. p. 411. 



VOL. XXXIX. 



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