1 86 SIGNIFICANCE OF MALFORMATIONS IN ORGANOGRAPHY 



Occasionally a generation may be passed over. Thus the seeds from two fasciated 

 capitula of Taraxacum officinale produced in the first year only normal individuals, 

 but in the second year ten fasciated inflorescences appeared upon the same plant, 

 and in subsequent generations as many as 30% of the inflorescences were fasciated. 

 No doubt external influences are of importance ; only well-nourished examples 

 with luxuriant growth show fasciation ] , a fact which is quite conformable with 

 \vhat will be stated below. 



2. Obligate torsion 2 . By this term A. Braun designated the twisting of 

 stems caused by the concrescence of leaves in a slightly extended spiral line. 

 This occurs as an abnormality in plants in which the leaves are normally whorled ; 

 if the position of the leaves becomes spiral and they unite at their base, they 

 form around the stem an imbricate tunic. As the stem elongates it must, so 

 far as possible, unroll the spiral line, and it twists itself in the opposite direction. 

 De Vries was able through the abundance of the material at his disposal to 

 prove the correctness of Braun's explanation of obligate torsions; before his 

 time the isolated cases which were found in nature were all the material available. 

 Once it was proved that obligate torsions could be inherited, numerous examples 

 for investigation were obtainable, and thus the conditions under which the mal- 

 formation occurs were determined. We have learned therefrom that weak seedlings 

 are not such favourable subjects for obtaining perfect examples of obligate torsions 

 as strong well-nourished plants in which other malformations, such as pleiomery 

 of cotyledons and fasciation, readily appear. 



3. Inherited sterility of maize 3 . In a cultivation of maize there appeared 

 completely sterile, altogether unbranched plants. If this habit were inherited we 

 should have a condition quite comparable with that of double-flowered plants 

 which are sterile themselves but are descended from single-flowered plants possess- 

 ing the ' tendency ' to develop double-flowered progeny. An almost sterile plant 

 was selected, one bearing cobs with only very small grains ; nineteen per cent, 

 of the progeny was entirely sterile, whilst the progeny of other stronger examples 

 showed only a few cases of sterility. 



4. The malformation which occurs in Vitis vinifera and is known as 'Gabler' 

 may be added to the above 4 . In this the tendrils become vegetative shoots and 

 in consequence the formation of flower is entirely suppressed. This kind of mal- 

 formation occurs occasionally also in the normal vines, but in the true ' Gabler ' 

 a permanent race-feature is developed which repeats itself in cuttings. Upon 

 its transmissibility through seed in a manner analogous with the cases previously 

 described nothing is known. 



5. An abnormal form of Myosotis alpestris, to which Magnus has directed 



1 Less well-nourished individuals give also more reversion to the normal form. 



2 De Vries, Monographic der Zwangsdrehungen, in Pringsh. Jahrb. xxiii ; Id., Eine Methode 

 Zwangsdrehungen aufzusuchen, in Ber. der deutsch. botan. Gesellsch. xii. 



3 De Vries, Steriele Mais alserfelijk ras, in Bot. Jaarboek, Dodonaea, ii (1890) ; Id., Over sterile 

 Ma'is-planten, ibid, i (1889). 



4 E. Rathay, Uber die in Nieder-Osterreich als ' Gabler ' oder ' Zweiwipfler ' bekannten Reben. 

 Klosterneuberg, 1883. 



