114 MR. W. €. WORSDELL ON THE 
the extrafascicular rings which occur in four genera of modern Cycads. That is to say, 
it is in this form of isolated, concentric, or partially concentric strands that the extra- 
fascicular rings, or at least the first of these, make their earliest start in development in 
the primary node; the collateral structure at a later stage, during the subsequent 
development and growth of the plant, assuming complete sway. 
In the above-mentioned paper on Encephalartos I stated that these outer concentric 
strands are homologous with the so-called **anomalous strands ” described by Scott * in 
Medullosa anglica; they are also, in like manner, homologous with the extrafascicular 
strands figured and described by Weber & Sterzel + in certain species of Medullosa. 
And my fig. 3 (Pl. 15) may be aptly compared with the strand marked 2 in fig. 2, pl. 4, of 
the last-named paper, which represents a fragment of the stem of Medullosa Leuckarti, 
Gópp. & Stenz., and which I have reproduced in my fig. 4. 
The upper region of the root exhibits a ¢riarch structure. At a lower level, where 
its diameter is smaller, it becomes ¢etrarch; still lower again ¢riarch, and finally diarch. 
In this narrowest portion of the root an internal periderm occurs. 
Cycas SEEMANNI, Al. Br. 
Through the kindness of Prof. F. W. Oliver I was enabled to examine a slide at 
University College containing, amongst others, a transverse section through the primary 
node, in the region exhibiting root-structure, of this plant, The structure there shown 
confirms in a remarkable manner the conclusion I have from time to time drawn and 
put forward as a result of an examination of sections from the same region of the 
vegetative axis in Macrozamia Fraseri, Miq., M. Denisonii, F. Muell., Encephalartos 
horridus, Lehm., and Cycas revoluta, Thunb. 
In my paper on Macrozamia Fraseri, Miq., I ventured to draw the inference, from the 
observation of small inverted strands (i. e. strands whose xylem and phloem are inversely 
orientated as compared with the normal condition) occurring here and there, quite 
infrequently on the ventral side of some of the extrafascicular collaterally-constructed 
rings, that the latter derive their origin, through descent with modification, from the 
concentrically-constructed rings of vascular tissue of the fossil Medulloseæ. 
In the plant under consideration these inverted strands once more make their 
appearance, but this time in greater abundance, and with a distinctness which leaves 
no doubt as to their position and orientation. After considering the structure which 
is here incontrovertibly presented to us, there can no longer remain, in my own mind, 
a shadow of doubt that the four genera of modern Cycads which exhibit the character of 
extrafascicular rings of vascular tissue are directly descended from some group of 
plants amongst the Cycado-filices, like the Medullosee, which possess similar extrafascicular 
rings in their stems, but (well-nigh universally) of a concentric structure. 
Of extreme interest, however, and strongly confirming my conclusions, is the case of 
Medullosa stellata var. gigantea, which already, at that remote epoch, had advanced 
* « On Medullosa anglica, a new representative of the Cycado-filices,” Phil. Trans, Roy. Soc., B. vol. 191, 1899, 
pp. 81-126. 
+ Beiträge zur Kenntniss der Medulloseæ, 1896. 
