94 SCIENCE PROGRESS. 



no new morphological element is to be found. The com- 

 bination of already existing properties is new, but the 

 properties thus combined remain themselves constant, like 

 the fragments of coloured glass which give rise to the 

 changing pictures of the kaleidoscope. Malformations 

 resulting in the formation of compromises between two 

 organs are the very frequent consequence of this, thus 

 Pevritsch has observed in Valeriana all intermediate stagfes 

 between bracts and pappus-rays instead of bracts only, and 

 the same between bracts and petals. 



If then nothing new arises during such malformation, 

 but only another combination of parts already present, we 

 are justified in concluding that it is necessary to be cautious 

 in assigning phylogenetic significance to malformations as 

 has very often been done. Admitting that many of the 

 latent capabilities which exist in plants are called into action 

 in an augmented degree by malformation processes, the 

 question is only one of the revelation of something which 

 was really existent though in an attenuated condition, and 

 not of a change in the organs as a whole. This occurs 

 when, for instance, leaflets appeared instead of ovules in 

 chloranthic flowers. The characteristics of ovules, the 

 embryosac, and so on, have disappeared. But, on the 

 other hand, when the bracts of the inflorescence of a 

 Crucifer, for instance, are developed, this may, upon com- 

 parative grounds, be regarded as a reversion to type. 

 The same is true of the fact observed by Treub and others, 

 that when gall-formation occurs in the flower-heads of 

 Hieracium umbellatnni, Calyces in all stages from the 

 normal pappus of the flower to the occurrence of five 

 separate green leaflets with regular venation were found. 

 But such an inference can only be justified by comparison 

 with allied forms, since it is probable that there are also 

 latent tendencies which were never developed in the an- 

 cestral forms. 



Thus, in Selaginella pentagona A. Braun and Strasburger 

 have noted remarkable gall-formations, externally resembling 

 bulbils. These have six rows of similarly formed leaves, 

 whilst, as is well known, the leaves of Selaginella are nor- 



