CYCADALES 



9 



and tuberclelike rootlets. The apparently dichotomous branch- 

 ing of these bodies has led to the general statement that the sec- 

 ondary roots of Cycads 

 branch dichotomously, 

 but the dichotomy even 

 in this case is only ap- 

 parent, for the true 

 apex, although com- 

 pletely checked in ac- 

 tivity, is evident be- 

 tween the branches. In 

 1872 Keinke 6 an- 

 nounced the presence of 

 an endophytic alga in 

 these tuberclelike root- 

 lets, which he referred 

 to Anabaena, and in 

 1894 Schneider 19 pub- 

 lished an account which 

 gave much fuller de- 



FIG. 6. The so-called " root tubercles " of Cycas 



., -.^ revoluta; about natural size. After LIFE. 



tails. Irom a recent 



paper by A. C. Life, 31 the following facts are obtained. 

 It appears that the soil about the roots is full of low algal and 



fungous forms, and these 

 forms are found also thickly 

 clothing the roots. At the 

 very inception of a branch 

 bacterioid forms effect an 

 entrance, and are found in 

 abundance in the cells of the 

 apical region. Presumably 

 through their activity ex- 

 crescent growth begins, and 

 a definite zone of cortical 

 cells is disorganized, result- 

 ing in a cortical chamber 

 about midway in the cortex 

 (Fig. 7). Upon the surface 



numerous lenticel-like openings are developed, and connect with 



the cortical chamber, which soon becomes filled with Nostoc 



FIG. 7. Cross section of a " root tubercle " 

 of Cycas revoluta. showing the algal zone. 

 After LIFE. 



