64 Gregg. — Anomalous thickening in 
of the primary structure, and of the normal products of 
thickening, in the roots of Cycas revoluta , and also in species 
of Dioon , Encephalartos , and Zamia . The mode of develop- 
ment which he describes essentially agrees with that of the 
roots of the Conifers ; the case of the diarch root of Cycas 
revoluta , which he describes very fully, agreeing for example 
with such a root as that of Taxus. The subsequent occur- 
rence of abnormal growth is mentioned by him in the following 
words ( 1 . c. pp. 598-9) : ‘ Mit dem hoheren Alter der Wurzel 
erlischt endlich die Thatigkeit der Cambiumschichte, und 
beginnt gerade wie in dem Stamm ausserhalb des Bastes die 
Ausbildung einer zweiten, und schreitet das weitere Wachsthum 
in voller Uebereinstimmung mit dem des Stamm’s fort.’ 
No further details however are furnished on this part of the 
subject, nor have later investigators, so far as I have been able 
to ascertain, added anything to our knowledge of the point in 
question. The writer who in recent times has dealt most 
fully with the roots of Cycadeae is Reinke ; to him is due our 
knowledge of several points of interest, more especially the 
curious changes in the roots due to the presence of nostoc- 
colonies within their tissues ; a further observation of special 
interest was Reinke’s discovery 1 of two peridermal layers in 
Cycas circinalis , one derived in the normal manner from the 
pericambium and the other arising externally at the peri- 
phery of the cortex 2 . No observations, however, relating to 
the abnormal development of secondary wood and bast are 
recorded by this investigator. In view of the extreme 
scantiness of our knowledge of anomalous thickening in roots 
of Cycas, the following observations on the roots (preserved 
in alcohol) of some seedlings of Cycas Seemanni grown in the 
Royal Gardens, Kew, from seed obtained from Fiji, may not 
be without interest. The material of Cycas Seemanni , Al. 
Braun, which is probably a geographical form of C. circinalis , 
contained five or six good specimens of roots varying in 
1 Reinke, Morphologische Abhandlungen, 1873. 
2 It may be mentioned in passing that I have observed the same condition in the 
root of Cycas revoluta . 
