The Development of Pilularia globulifera, L. 
BY 
DOUGLAS HOUGHTON CAMPBELL, Ph.D. 
With Plates XIII. XIV. XV. 
HE Pteridophytes, standing as they do between the non- 
X vascular plants and the Phanerogams, are in many ways 
of especial interest to the botanist, and since the first work of 
Hofmeister 1 on their embryology, there has been a long series 
of works of greater or less value bearing upon the subject. 
Owing to the imperfect methods of the earlier investigators, 
it was impossible to satisfactorily make out much that is 
rendered relatively easy by the employment of the more 
improved methods of to-day, this being particularly the case 
with the study of the early stages in the germinating spores of 
the heterosporous forms. 
In undertaking the work, the results of which are embodied 
in the accompanying paper, two objects were had in view: — 
ist, the investigation of the life-history of Pilularia globu - 
lifera ; and and, to determine how far the paraffin imbedding- 
process was of practical application in the study of vegetable 
embryology. In regard to the first point, the results are given 
at length in the following pages, and will not be recapitulated 
here ; touching the second, it will be sufficient to say that the 
perfection of the sections thus obtainable, and especially the 
fact that series of sections can be made, will convince any one 
who has seen it that this method, or at any rate some 
method of imbedding by which similar serial sections can be 
made, will in future be as essential for the study of the em- 
bryology of the higher plants as it has come to be regarded in 
1 Hofmeister, Vergleichende Untersuchungen. 
[Annals of Botany, Vol. II. No. VII. November 1888.] 
R 
