CYCADALES 



of Cycas, some of which carry the crown of leaves upon a col- 

 umnar trunk 3 to 4 meters, or sometimes even 12 meters 

 high, while the Australian Cycas media reaches a height 

 of over 20 meters; but, in the majority of cases, the stem is 

 short and stocky, assuming the so-called tuberous form. In 

 fact, all the stems when young have the tuberous form, and the 

 difference between the two types consists in the one retaining 

 this form and the other becoming columnar. Branched forms 

 are rare in nature, but seem 

 to be more common in cultiva- 

 tion. We are informed that 

 wild plants are apt to branch 

 after they reach a certain age. 

 Until recently, the ac- 

 counts of the histology of the 

 stem have been derived in the 

 main from species of Cycas, 

 Encephalartos, and Stangeria. 

 A historical resume of the sub- 

 ject was published by Wors- 

 dell ^^ in connection with his 

 work upon Macrozamia, the 

 substance of which is as fol- 

 lows: In 1829 Brongniart^ 

 gave some account of the anat- 

 omy of the stem of Cycas rev- 

 oluta, refuting the idea that 

 Cycadean stems are similar to 

 those of Monocotyledons, and 

 pointing out their true Gymno- 

 sperm character. He claimed, 



however, that there is no phloem, and that xylem is the only 

 vascular tissue developed. In 1832 Von Mohl ^ published an 

 account of the stem anatomy of Cycas and two species of ]!Jn- 

 cephalartos (referred at that time to Zamia, and known as Z. 

 latifolia and Z. horrida). In one of the species of Encephalartos 

 Chis Z. latifolia, but an African Encephalartos not to be con- 

 fused with Z. latifolia Loddiges) he discovered the meshwork 

 of vascular bundles in the pith, and the fact that single bundles 

 traverse the pith rays and enter the cortex. In 1841 Miquel^ 



g^V/Sf-c~,.s;^i7---s-/;/rSP' 



Fig. 2. — Cycas media in the middle and at 

 the right; Cycas Normanbyana at the 

 left.— After F. Von MtlLLEK. 



