404 BOTANICAL GAZETTE [DECEMBER 
Now, at the time the protoxylem elements appear, I did not 
find, in the species examined, the cells of the endodermis cor- 
radial with those lying centrad. It is true that in younger 
stages the cells in this region are in radial rows; but nearer still 
to the punctum vegetationis this is approximately true of all the 
cells of the stem. At this earliest stage one would hesitate to 
say, because certain cells were corradial, that they were therefore 
division products of the same mother cells; so Zenetti’s con- 
clusion, based on this sole argument, scarcely seems conclusive, 
even granting the correctness of his observation. If, too, such 
a conclusion were correct there would be the curious anomaly of 
certain phloem and cortical tissues having a common origin. 
Evidently the study of transverse sections cannot settle the 
matter. To attempt to follow these layers upwards is obviously | 
only possible in median longitudinal sections. But in the stems 
of the Osmundaceae the leaf traces are exceedingly numerous, 
and at the growing point are closely packed together, and 
appear before the tissues of the cauline central cylinder become 
at all differentiated. Hence, no matter what be the plane of 
section, the endodermis cannot be traced continuously very far 
anteriorly to the point at which it is differentiated, for a leaf 
trace is certain to intervene; andI found it quite out of the 
question to pick out an undifferentiated endodermis on the side 
of the leaf trace turned towards the apex. Therefore, every 
attempt failed to refer the endodermis and the rows of cells 
‘occupying the place of the pericycle” to the same initial layer. 
The typical protophloem, and the “quergestreckte Zellen e 
begin to be differentiated simultaneously with the appearance of 
the protoxylem. They are best examined in tangential sections. 
Their walls at this time become pitted, and their contents much 
less granular than those of the surrounding cells. Here, as in 
the maturer parts of the stem, there appear to be no differences 
between the typical protophloem and the “quergestreckte Zel- 
len.” Their relation to the leaf traces seems to explain their 
irregularity in orientation. Immediately below the point of ori- 
gin of a leaf trace they are arranged with their long axes parallel 
