ii2 PROBLEMS OF GENETICS 



the results from the biennis-muricata experiments before us, 

 it is natural to suspect that we may here again have to recognise 

 a process of allocation of different factors to the male and female 

 sides in laeta and velutina. That some such system is in operation 

 becomes the more probable from the new fact which de Vries 

 states in describing the group of characters which he calls conica, 

 namely that this type is the same as that of velutina. 



There are many collateral observations recorded both by 

 de Vries and others which have a bearing on the problems, but 

 they do not yet fall into a coherent scheme. For example, we 

 cannot yet represent the formation of laeta and velutina from the 

 various species fertilised by Lamarckiana cf . That this is not 

 due to any special property associated with the pollen of La- 

 marckiana is shown by the fact that a species called Hookeri 

 gives laeta and velutina in both its reciprocal crosses with La- 

 marckiana (de Vries, 1909, p. 3), and also by the similar fact that 

 Lamarckiana 9 fertilised by the pollen of a peculiar race of 

 biennis named biennis Chicago throws the same types. Before 

 these very complicated phenomena can be usefully discussed 

 particulars must be provided as to the individuality of the various 

 plants used. This criticism applies to much of the work which 

 de Vries has lately published, for, as we now know familiarly, 

 plants to which the same name applies can be quite different in 

 genetic composition. 



Attention should also be called to one curiously paradoxical 

 series of results. When the dwarf "mutant" of Lamarckiana 

 which de Vries names "nanella" is used as father on muricata, 

 Fi consists of laeta and velutina in approximately equal numbers. 

 Both forms breed true to their special characteristics, but 

 velutina throws dwarfs of its own type, while laeta does not 

 throw dwarfs. Subsequent investigation of the properties of 

 these types has led to some remarkable conclusions, and it was 

 in a study of these plants that de Vries first came upon the phe- 

 nomen of dissimilarity between the factors borne by the male 

 and female cells of the same plant, a condition which had been 

 recently detected in the Stocks as a result of Miss Saunders's 

 investigations. The details are very remarkable. We have 



