242 
W. C. Worsdell. 
THE RHIZOPHORE OF SEL AGIN ELLA. 
By YV. C. Worsdell. 
[Text-Figs. 15, 16J. 
Y recent observation of abnormal forms of the rhizophore in 
various species of Selnginella has led me to write on the 
subject of the morphology of this organ, about which there has been 
so much controversy and divergence of opinion. 
The rhizophore of Selnginella, the tubers of Dioscoreaceae, the 
submerged vegetative portion of the plant-body of Utricularia, the 
ovule of the Angiosperms, and the sporangium of the Vascular 
Cryptogams are examples of organs, the ascription to which, owing 
to their peculiar structure, position, &c., of a place in any one of 
the usually accepted morphological categories of shoot, root and 
leaf has always been a matter of considerable difficulty ; and this 
difficulty has been for some botanists so grave that they have, as it 
were, cut the Gordian knot and placed the doubtful organ in a new 
category, the characteristics of which are those of the particular 
organ itself! 
But the view that there can exist at the present day, at this 
very late period of plant-evolution, organs which are still, so to speak, 
undifferentiated, or that any group of plants can give rise to new 
organs which represent in themselves a fusion of distinct types of 
organs which have already, time and again, been evolved during the 
past history of the race,—is to my own mind in the highest degree 
improbable. If we consider, for present purposes, the vegetative 
organs alone, we find that the tendency in all groups of plants, 
except those which, like the Fungi, have become adapted to a 
saprophytic or parasitic mode of life, is towards the differentiation 
of the plant-body into three, and three only, stereotyped sets of 
organs resembling what we are accustomed to speak of as shoot, 
leaf, and root. The highest forms in the three great classes of Algae 
shew this tendency. It does not tell against, but in favour of, my 
view that here and there in the Algae there is no sharp distinction 
between shoot and leaf, for it is precisely in this group that the 
evolution of this differentiation has taken place. Indeed this group 
represents the foundation upon which all higher groups have been 
established, and it is only what we should expect that here and there 
the distinction between shoot and leaf is not an obvious one. Such 
a resemblance between the two categories of organs, we should, 
however, never expect to find in any group higher than the Algae; 
