compared with other genera of Cycadeae. 603 
Encephalartos horridus , Dioon edule, and Zamia muricata. 
In the two latter genera he finds no anomalous structure 
present. 
Costantin and Morot 1 , who investigated Cycas siamensis , 
with regard to the structure of the pericycle, state that it is 
in this tissue that the anomalous rings have their origin. 
Count Solms-Laubach 2 has investigated the stem-structure 
* of Stangeria paradoxa. The chief part of the paper is taken 
up with an elaborate description of the course of the ring of 
vascular bundles from the peduncle, which traverse the pith 
of the main stem for some distance before joining on to its 
vascular system. In this plant he finds no trace of any 
anomalous secondary thickening. The whole structure, with 
the exception of the medullary position of the cylinder from 
the peduncle, which is a phenomenon occurring also in other 
Cycads, is straightforward and normal. 
Strasburger 3 , in his work on the vascular tissues, gives an 
accurate account of our present knowledge of the anatomy of 
Cycas, but so far as the stem is concerned has not extended 
his investigations to other genera. 
General Structure. 
The chief peculiarity in Cycadean stems, which was recog- 
nized and described by former writers, is the presence of 
anomalous rings of secondary thickening outside the normal 
zone. This character, however, has hitherto been described 
for two genera only, viz. Cycas and Encephalartos ; other 
genera, as Zamia , Dioon , and Stangeria, are said to be with- 
out this abnormality. The genus Macro zamia has apparently 
not yet been investigated. 
Having had the opportunity of examining an old stem of 
Macrozamia Fraseri, Miq., of more than one foot in diameter, 
grown at Kew, I was able to determine that the same anomaly 
1 Bulletin de la Societe Botanique de France, XXXII, 1885. 
2 ‘ Die Sprossfolge der Stangeria und der iibrigen Cycadeen,’ Bot. Zeitung, 1890. 
8 Hist. Beitrage, III, p. 151, 1891. 
S S 2 
