PREFACE 



Ever since the appearance of Hofmeister's remarkable investi- 

 gations upon the Archegoniatae, the ever-increasing list of works 

 upon these plants has borne witness to the interest felt by 

 botanists in their structure and development. From time to 

 time the results of these investigations have been collected, but 

 for the most part this has been done in general text-books, 

 where want of space has naturally made it impossible, often, 

 to give much more than a mere summary of results. 



The last ten years have been especially noteworthy, not 



only for the number of investigations upon the Archegoniates, 



but for the extension of our knowledge to many forms which 



were hitherto but very imperfectly known. These results have 



come from two sources : first, the extension of the field of 



research to the Tropics, through the establishment there of 



experiment -stations and properly equipped laboratories in 



connection with botanical gardens ; second, the advances in 



histological methods, especially the use of the microtome in 



embryological studies, which have made possible the accurate 



determination of many important structural details hitherto but 



CD very unsatisfactorily made out. The application of these more 



«— exact methods of research have made necessary, also, a careful 



• review of the results of earlier investigations, and the correction 



of mistakes due to imperfect manipulations. 

 <£ The results of these later researches have only begun to 

 find their way into the text-books, and the present work was 

 undertaken mainly for the purpose of presenting, in somewhat 

 detailed form, a resume of the substance of the great mass of 

 literature upon the subject which has accumulated, and much of 



