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THE TUBER-LIKE ROOTLETS OF CYCAS REVOLUTA. 
CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY. 
A, CC. LF rR. 
[WITH TEN FIGURES | 
THE coral-like outgrowths in connection with the roots of 
Cycas revoluta have long been known. In 1871 and 1872 Reinke? 
published an account of them and described the associated endo- 
phytic alga, which he referred to Anabaena (fig. 70). In 1894 
Schneider? published further details, and referred to these struc- 
tures as root tubercles. My own work was begun at Indiana 
University and continued at The University of Chicago. 
The occurrence of these structures in Cycas revoluta is by no 
means uniform in greenhouse plants, as they are abundant in 
some cases, few in others, and entirely lacking in still others. 
They are connected with the upward rising rootlets, usually 
spreading radiately from the apex and just behind it, and are 
most abundant at or very near the surface of the ground, but 
may occur several inches beneath it. They vary considerably in 
Size, but are always larger than the normal roots of the same 
age, and by branching may form clusters 2.5°™ or more in diam- 
eter (fig. 7). 
This branching is apparently dichotomous and such a claim 
has been made for these rootlets. According to Reinke? this fact 
indicates relationship with the Lycopodiales, while Schneider’ 
ee that it is a case of atavism. If by true dichotomy it is 
*Einige Bemerkungen iiber das Spitzenwachstum der Gymnospermen Wurzel. 
Gott. ‘tick ble 530. 1871. 
Parasitische Anabaena in Wurzeln der Cycadeen. Gott. Nachrichten 107. 1872. 
* Mutualistic symbiosis of algae and bacteria with Cycas revolute. Bot. Gaz. 
19: 25-32. pls. 3,4. 189 
4 3 Beitrag zur Kenntniss der Gymnospermwurzel. Just’s Bot. Jahresb. 1: 205-207. 
1673. 
Igor] 265 
