THE ORIGIN OF THE VASCULAR PLANTS. 



ABOUT forty years ago there appeared a series of 

 publications that marked an epoch in the study of 

 vegetable morphology. These were the remarkable papers 

 of the German botanist Hofmeister, in which the compara- 

 tive morphology of what are now known as the Arche- 

 goniatse was discussed for the first time from the standpoint 

 of the evolutionist. Hofmeister showed that the Mosses 

 and Ferns belonged to one natural series, and that the 

 Phanerogams were connected by the Gymnosperms directly 

 to the higher Pteridophytes, and that the terms " Cryptogam" 

 and " Phanerogam " must be discarded, at least in their old 

 signification, as marking two radically different types of 

 plants. 



The result of Hofmeister's work was the arousing of 

 extraordinary interest in the study of the structure and 

 development of the Archegoniatse and the publication of a 

 great number of investigations upon these forms. It is not 

 necessary to mention here the long list of eminent botanists 

 whose names are connected with these investigations which 

 corrected and added to the splendid results of Hofmeister's 

 pioneer efforts. Within the last few years a still farther 

 impetus has been given to this subject by the great 

 improvements in histological methods which have made it 

 possible to solve many problems which quite baffled the 

 earlier botanists. This has been especially the case in the 

 study of the so-called heterosporous Pteridophytes, where the 

 •development of the earlier stages goes on within the spore, 

 but applies also to the exact study of all the delicate tissues. 

 These improvements consisted first in the application of the 

 careful methods employed by zoologists for preserving and 

 staining tissues, and secondly the use of the microtome for 

 sectioning delicate organs. Undoubtedly the name of 

 Strasburger must lead the list of those who have been con- 

 cerned with the improvement of histological methods. 



The study of the Archegoniatae has an especial interest, 



