Anomalous thickening in the roots of Cycas 
Seemanni, Al. Braun. 
BY 
W. H. GREGG, B.A. (Dublin), 
Surgeon- Major, Bengal Army. 
With Plate VI. 
W HILE working in the Jodrell Laboratory, Kew, under 
the direction of Dr. Scott, and with material which 
Professor Bower kindly placed at my disposal, I found some 
abnormal thickening in the roots of Cycas Seemanni which 
does not appear to have been previously observed. Abnormal 
thickening in the stems of Cycas, Dioon , Zamia, and En- 
cepkalartos , has been well worked out by Mettenius and 
others 1 . The abnormality consists in the appearance of 
successively renewed zones of cambium outside the normal 
ring — each of these in turn continues its activity for a limited 
period, and then passes over into permanent tissue, while 
the process of thickening is carried on by a new zone 
appearing nearer the periphery of the stem. In the case of 
Cycas there is a further abnormal process consisting in the 
relatively late appearance of distinct cortical bundles— each of 
which undergoes a certain amount of thickening by means of 
a cambial ring of its own. As regards the roots of the Cycads 
our knowledge is far less complete. The researches of Met- 
tenius have made us fully acquainted with the development 
G. Mettenius, Beitrage zur Anatomic der Cycadeen, i860. De Bary, Com- 
parative Anatomy of the Vegetative Organs of the Phanerogams and Ferns, Eng. ed., 
1884. 
[ Annals of Botany, Vol. I. No. I. August 1887. ] 
