of Vascular Strands in A ngiopteris evecta. 375 
We have ourselves been led to form a somewhat different 
conception of the relations existing between the various 
branches of the vascular system, as will become apparent 
later on. The chief respects in which we differ lie perhaps in 
the direction of greater simplicity, for a study of the youngest 
plants shows that the complex arrangements met with in the 
older specimens are in reality susceptible of easy explanation. 
The primitive type can, when once understood, be readily 
discerned, in spite of the disguise produced by the remark- 
able degree of anastomosis and branching which the vascular 
strands undergo in these plants. 
The method adopted by us in studying the relations and 
the development of the vascular skeleton in the young sporo- 
phytes of various ages has been as follows. Entire plants 
were cut by means of the microtome into serial sections, care 
being taken that all the sections were preserved and retained 
in their proper order on slides. From these the vascular 
tissue has been built up in the form of wax models. Sheets 
of wax are prepared of a thickness appropriate to the thick- 
ness of the sections, and the degree of magnification employed, 
and a tracing made on successive sheets of the vascular tissue 
in every section in its proper order. The drawings were then 
cut out, due care being taken to preserve the proper orienta- 
tion, and the wax sections mounted one above another were 
then held in their places by inserting warmed needles and by 
carefully fusing the edges. Models prepared in this way, and 
with due precautions, are extremely accurate, and there is 
no danger of either missing or confusing even minute details 
of anastomosing and branching, such as must attend the most 
careful dissection. And it is of course far more easy to 
interpret such models, all the parts of which are true to scale, 
than is the case with a series of drawings however carefully 
prepared. The actual process of tracing and building up the 
models often involving several hundreds of sections for one 
plant, is doubtless tedious, but the clearness and certainty of 
the results more than repay the labour expended upon them. 
