562 S topes. — On the Double Nature of the Cycadean Integument 
supposed 1 , and for the sake of the present argument I will summarize the 
most important of these points. 
The first thing to be established was the fact that the inner of the two 
series of vascular bundles penetrating the ovule and generally termed the 
‘micellar’ series was truly integumentary. Facts supporting this were 
found in a large number of species, the most important case being that 
of Cycas circinalis , where not only are these bundles definitely seen to run 
in the inner layers of the integument, which is clearly marked off from the 
nucellus, but they are found to be continued in the integument almost 
to the micropyle, passing beyond the level at which the nucellus becomes 
free from the integument. The nucellus itself was found to be entirely 
devoid of vascular tissue throughout. 
In addition, it was found that within the stone are tissues of consider- 
able importance, in which this inner series of bundles runs and which form 
a very definite inner layer to the integument, although this has been 
frequently overlooked owing to its liability to get crushed in the ripening 
seed. 
The integumentary nature of the inner vascular strands being 
established, the course of the bundles of the two systems was examined 
in detail, the result being the recognition that through all the various 
specific and generic variations which tend to mask it more or less 
completely there runs a central plan for their arrangement. This may 
be shortly described as consisting of a strand which gives off a series 
of bundles to the outer flesh of the ovule-coat, and continues its way, 
dividing up to form the inner series which may be further supplemented 
from the outer series. This is seen best in Cycas , Dioon , and Zantia , 
though in many cases the bundles appear to come off at the same level. 
In anatomical structure the main supply bundle is usually either completely 
concentric or has a strong tendency in that direction ; the bundles given off 
to the outer flesh are collateral and orientated with the phloem outwards 
and with a considerable development of centripetal xylem ; the strand 
continuing to supply the inner system has a strong concentric tendency, 
as have also those auxiliary ones derived from the outer series ; the actual 
bundles of the inner series are orientated in the same sense as the outer, 
but with little, if any, centripetal xylem and seldom with definite spiral 
protoxylem. 
These facts suggested a comparison with Lagenostoma and its cupule, 
in which the details of vascular arrangement and structure are strikingly 
parallel. 
Now that all the facts for Lagenostoma are before one, this comparison 
appears to be justified in the main. One is not ‘arguing in a circle/ but 
rather placing the facts from either side so as to act as props which enable 
1 Stopes, loc. cit. 
