242 
ische Untersuchungen iiber die Differenzen im Primarem Bau der 
Stengel und Rhizome Krautartiger Phanerogamen” by Wladys- 
law Rothart, in which the author suggests a principle of classi- 
fication which he says rests on a morphological-anatomical 
basis, and claims for this method a great superiority over that 
based on the physiological-anatomical characteristics. He states 
expressly that in this system the mischievous practice of consid- 
ering the probable function of an element in deciding to which 
class of tissue it belongs has been carefully avoided. 
According to this author the wood elements are first divided 
into two classes, Desmogen and Bythom, or “strang” and “grund” 
tissue. The former he divides into four classes, the latter is not 
divided. Only the first two divisions of the Desmogen are of 
interest in this connection, namely: Inom and Tracheom. As 
Inom are considered all those desmogenic elements containing 
simple pores or none. As Tracheom all those containing bor- 
dered pores; this class includes the ring and spiral, as well as 
the ‘‘netz-gefasse,” (reticulated tracheze) the ring and spiral wall- 
thickenings being considered only modifications of the bordered 
pore, and the reticulated trachez a transition form between these 
two. This division is based principally on the common sculpture 
of the cell wall, which he says may be considered an infallible 
criterion. a 
It is well known that in many instances a single member of 
a trachea which borders on other trachez as well as on cells of 
the medullary ray and libriform tissue contains large and num- 
erous bordered pores on the side adjacent to the other tracheex, 
while that part of its wall bordering on the cells of the medul- 
lary ray or libriform tissue contains simple pores, and these in 
comparatively small numbers. In these cases the infallibility of 
the wall-sculpture does not appear sufficient to decide the class to 
which the element belongs. | Very often in the course of this 
work were found single tracheal tubes; that is, a tube consisting 
of many members was found isolated from other trachez, and as 
far as could be traced it contained only simple pores. It is not 
improbable that where such tubes joined other trachea otherwise 
than by a dissolved partition wall, the usual bordered pores occur- 
red, but as far as the section extended these members. were entirely 
