68 



PRINCIPLES OP PLANT-TERATOLOGY. 



porrifolius) . One cannot say whether this is true 

 forking or a case of abortion of the main root with 

 hypertrophy of the two lateral roots; either pheno- 

 menon might yield the same appearance. 



The tuberous roots of Orchis and Ophrys, with their 

 apical division into a number of separate tips, may be 

 regarded as normal examples of fasciated roots ; the 

 vascular structure supports this, for in the tuber- 

 lobes there may be present more than one vascular 

 cylinder. 



The apogeotropic, coralloid respiratory roots of 

 Cycads must probably also be regarded as instances 

 of normally fasciated roots. 



Miss M. Rathbone sent the author some aerial roots 

 of the ivy (Hedera Helix) from Neston, Cheshire, 

 which showed, better than he has seen elsewhere in 

 the vegetable kingdom, examples of dichotomy or 

 forking and of fasciation, with gradual transitions 

 between the two phenomena. Caspary in 1882 ob- 

 served the same phenomenon in this plant and gives a 

 beautiful figure of it. At the point of its attachment 

 to the stem the root is quite narrow and apparently 

 cylindrical in contour ; but Caspary, in studying the 

 development, found that the section of the root at 

 this point was really oval in outline, and that the zone 

 of tissue in the stem from which it arises is excep- 

 tionally broad in the tangential direction, the root 

 thus arising from the first as a more or less flattened 

 organ ; however, as growth proceeds the root expands 

 more and more in fan-like fashion. It may subse-« 

 quently fork neatly into two equal arms, one of which 

 may grow more rapidly than the other and fork again 

 equally ; or successive dichotomies may take place, one 

 arm, often, apparently, on the same side, developing 

 ahead and expanding in fan-like fashion, until at the 

 apex it appears to branch simultaneously into a 

 number of various-sized short branches; at the same 

 time the whole root, owing to unequal rapidity of 

 growth on the two sides, becomes slightly twisted 



