SIGNIFICANCE OF MALFORMATIONS 183 



the nucellus appears in a lateral position because that portion of the 

 primordium which was immediately below it has grown out into a leaflet. 

 In Fig. 107, 4, a further case is represented where the outer and inner 

 integuments were both laid down at the moment of the beginning of 

 phyllody, but the lower part of the primordium has become leaf-like 

 and grown out beyond the outer integument. We must also note that 

 frequently the ovule is replaced by a simple leaf if the phyllody has 

 started at a period when neither integument nor nucellus nor arche- 

 sporium were laid down. This extreme case shows how incorrect it is 

 to regard the phyllody as a reversion : the final result is a simple leaflet, 

 and it would be as absurd to regard this as the most primitive phylogenetic 

 stage of development as to recognize this when the characteristically formed 

 sporiferous leaf-portion of an Aneimia appears as a vegetative leaf if the 

 formation of sporangia is suppressed. The propagative organs, the origin 

 and development of which are involved in both cases, are entirely wanting, 

 and associated with this, and certainly in causal connexion therewith, 

 definite vegetative phenomena appear. That the primordium of an integu- 

 ment becomes a leaflet is no more reason for our requiring to consider 

 that it must have been such a body, than is the occurrence of a cell-group 

 which in phyllody frequently develops into a shoot in the axil of this 

 integument an argument for our considering that it has been a shoot. 

 The only conclusion we can draw from the phyllody is that the integuments 

 are formed out of carpellary substance, in other words, are outgrowths 

 of the carpels, and are the more able to take on a vegetative growth the 

 more the propagative organs that is. the nucellus are hindered in their 

 development. 



From what we have said it will be evident, without further remark, 

 that we must regard ovules which exhibit phyllody as crippled, diseased, 

 changed, formations. We can only consider it as an error to look upon 

 these kinds of malformations as reversions, and wonder that the assertion 

 should have been put forward that a leaflet upon which an arrested nucellus 

 sits, in which form the phyllody of the ovule sometimes appears (see 

 Fig. 107), is the exact homologue of a pinnule of a fern bearing a 

 sporangium or a sorus. As if an arrested papilla in which, so far as we 

 know, not even an embryo-sac is showing had the remotest shade of 

 resemblance to a sporangium! But it would take me too far were I to 

 follow further the erratic paths of doctrines of malformations. It is a much 

 more profitable exercise to go back again to the actual occurrences of 

 malformation and to elucidate the causes which condition the deviation 

 from the normal development ; and this question is the more important 

 as its solution can throw light upon the great problem of organic form. 

 The study of malformations is, as the investigations of De Vries show, 

 of special significance in the problems of inheritance and variation. 



