Relation to Cultivation . 
397 
on each sufficiently branched individual some of the branches 
are normal ; the normal branches are in fact usually more 
numerous than the abnormal. 
A few years ago I showed, in Crepis biennis, what results 
can be obtained by means of selection and cultivation in the 
case of fasciation 1 ; and in an earlier work 2 I demonstrated 
that from a few isolated individuals of Dipsacus sylvestris 
with twisted stems a breed can be produced by selection, 
such that the abnormality recurs annually in a larger or 
smaller number of the plants raised from seed. 
Such hereditary breeds or races afford the best material 
for comparative investigation of the conditions upon which 
the development of abnormalities depends. According to 
circumstances each successive generation is richer or poorer 
in so-called ‘ heirs ’ ; that is, in individuals which manifest the 
monstrosity. If the breed is in itself poor in heirs, that is, if 
it shows, even after careful annual selection of the seed-pro- 
ducers, only a small percentage of monstrous individuals, it is 
one which is obviously not suitable as material for such an 
investigation : but if, on the contrary, under normal conditions, 
[Note. The expression ‘ twisting of the stem,’ used above in the text, is intended to 
render into English the term * Zwangsdrehung,’ applied to this abnormality by Al. 
Braun (Monatsber. d. k. Akad. in Berlin, 1854), tor which there is no recognized 
English equivalent (see Masters, Vegetable Teratology) ; it might perhaps be well 
to adopt the term ‘ biastrepsis,’ proposed by Schimper (Flora, 1854, p. 75). The 
addition of a brief description of this ‘ Zwangsdrehung ’ or ‘ biastrepsis,’ in its 
characteristic form, may be of use to the reader. It occurs only in plants the 
shoots of which have opposite or whorled leaves ; the phyllotaxis becomes spiral 
instead of verticillate, the successive leaves of the spiral being connected by 
their bases. The effect of this cohesion of the leaf-bases is to prevent the normal 
elongation of the internodes, which therefore become spirally twisted and often 
much dilated and otherwise monstrous in form. When, as is sometimes the case 
(e. g. Dipsacus ), the stem is hollow, the pith-cavity is normally interrupted by 
diaphragms at the successive nodes ; but in the twisted stems the pith-cavity is 
continuous, the diaphragms of the normal stem being represented by a rib project- 
ing into the pith-cavity and following the course of the leaf-spiral. — Ed.] 
1 Sur les courbes Galtoniennes des monstruosites ; Bull. Scientif. de la France et 
de la Belgique (Giard), 1896, t. xxvii, p. 396. 
2 Monographie der Zwangsdrehungen, Pringsheim’s Jahrb. fiir wiss. Bot. xxiii, 
1891. See also, ‘ Eine Methode Zwangsdrehungen aufzusuchen,’ Ber, d. deutsch. 
bot. Ges. xii, 1894; and ‘ Bijdragen tot de leer van de Klemdraai,’ Kruidkundig 
Jaarboek, Dodonaea, iv, 1892, p. 145. 
