158 Scott. — On some recent progress in our 
adventitious roots an extensive work by Van Tieghem has 
recently appeared. His elaborate investigations appear to 
show that the facts are simpler than has been supposed, all 
Phanerogams agreeing in the origin of lateral roots from the 
pericycle, while in the Vascular Cryptogams they are formed 
entirely from the endodermis. To the latter rule, however, 
Lycopodium , Selaginella , and Isoetes are exceptions. 
It has, I think, been shown that active progress has been 
and is going on in the study of the vegetative anatomy of 
vascular plants. But this by no means exhausts the field of 
anatomical research. Very striking advance has recently 
been made in our knowledge of the internal structure of other 
classes of plants, and especially of the Algae and Muscineae. 
As regards the former class I need only call attention to the 
discovery of sieve-tubes in the larger brown Algae. The 
work of Parker, Will, and Oliver has shown that these 
structures are in all respects comparable to the sieve-tubes 
of the highest plants — a surprising result, which by itself 
is sufficient to show that the term ‘ cellular plants ’ can no 
longer be applied generally to the Algae. There can be no 
doubt, that further investigation will bring to light a very 
high differentiation of tissues in some of these plants. 
In the Mosses also we have learned, especially from the 
work of Haberlandt and the late Mr. Vaizey, that the tissues 
are much more highly organized than was supposed before. 
In many members of the class the existence of a conducting 
system, differentiated into tissues functionally corresponding 
to xylem and phloem, has been clearly demonstrated. 
The anatomy of the structures connected with reproduction 
is a branch of investigation which has in recent times been 
much neglected. The study of the development and structure 
of the complex fruits of the higher plants is an especially 
promising field of work, in which I am glad to say a beginning 
has already been made. 
The importance of anatomical characters in classification 
has been the subject of much discussion. It is, I think, 
perfectly evident, that internal structure must be taken into 
