COMPARATIVE ANATOMY OF THE CYCADACEEX. 119 
connection here and there with the main outer cylinder. What clearly indicates their 
vestigial ancestral character is the fact that many of them end blindly and that, in 
many cases, their tissues are not so well-developed as those of the bundles of the outer 
ting, staining but faintly with safranin and hematoxylin: a sure indication that such 
strands are on the road to extinction. 
The intrafascicular ring of strands is confined to the male cone in C. latifolia, Miq. ; 
it has also been mentioned by Scott * as occurring in the male cone of C. mexicana, 
Brongn. In other species it appears to be absent, this fact being on a par with that of 
the absence of medullary bundles from the vegetative axis of some species of Macrozamia 
(see supra). Thibout} describes and figures these medullary bundles, and I have 
myself { in a former paper brought them under notice. Their real significance and 
morphological value has, however, hitherto been completely overlooked. 
Several species of the genus Zamia and also Dioon edule, Lindl., have been studied 
from the point of view of their anatomical structure; but as the latter conforms in 
every respect with that of Cycadean genera, previously described by me, which do not 
possess extrafascicular vascular tissue in their stems (Stangeria, Ceratozamia), but 
only a single cylinder, it is not considered worth while to give any details of the structure 
of these genera. 
Microcycas, the very rare Cuban plant, is thus the only genus which remains 
uninvestigated ; its structure will, however, probably conform to that of Zamia. 
Summary. 
The chief results of this investigation are as follows :— 
1. The discovery in a fourth genus of Cycadaces, viz. Bowenia, of extrafascicular 
vascular tissue. This tissue, in the primary node, consists of both normally-orientated 
and inverted portions, such as is known to be characteristic of the strands occurring in 
the same region in Encephalartos and Cycas; but while in these latter genera the two 
portions of the strand are united together into a single, compact, concentric, or semi- 
concentric structure, in Bowenia they occur as distinct flattened strands. 
2, The occurrence of concentric or sub-concentric bundles in the cotyledon of Bowenia, 
a phenomenon heretofore only known to occur in Stangeria. 
3. A much-swollen stem of Bowenia exhibits concentric strands scattered in the 
cortex with inverted orientation of the parts of the vascular tissue composing them. 
These strands are correlated with the swollen parenchymatous character of the stem, 
and are merely physiological adaptations for the rapid conveyance of nutriment 
throughout the axis, and possess no morphological value. 
4. The occurrence in the region of the primary node of Macrozamia of extrafascicular 
concentric strands such as those found in the same region of the axis in Encephalartos 
* Scott, Ann. Bot. vol. xi. 1897, p. 412. 
+ Thibout : Recherches sur l'Appareil male des Gymnospermes, p. 24 (1896). 
+ Worsdell: ** The Vascular Structure of the Sporophylls of the Cycadacewe,” Ann. Bot. vol. xii. 1898, p. 232. 
