644 Beer . — Studies in Spore Development. III. 
the series of spore development. The different sporongia upon a strobilus 
are usually found to differ considerably from one another with regard to 
the stage of development which they have reached. In a single transverse 
section of a cone it is quite usual to find a sporangium containing mother- 
cells with nuclei in diakinesis (of the first division) lying side by side with 
another sporangium enclosing the spore-tetrads already formed. Besides 
this difference between the sporangia of a strobilus a good deal of variety 
can also, not infrequently, be seen amongst the spore mother-cells of one 
and the same sporangium. For example, a sporangium containing in one 
part tetrads in which the young, membraneless spores were just commencing 
to separate from one another, enclosed at another spot spore mother-cells 
still in the metaphase of the homotype division. 
Hofmeister (4) found a very similar variation to exist among the 
mother-cells of the sporangia of E. palustre. He wrote (pp. 283-4) : ‘ In 
the same sporangium of Eq. palustre there may be found mother-cells with 
the primary nucleus in the act of dissolution, others with two flattened 
nuclei, and others with four globular daughter nuclei ; there may also be 
found sets of four tetrahedral cells, individual daughter cells of a globular 
form, and lastly, others which already exhibit the transparent halo slightly 
developed.’ 
My material was fixed in absolute alcohol, alcohol and acetic acid 
mixture, and in Flemming’s solutions. Of these the stronger solution of 
Flemming gave the best results and was chiefly employed for this study 
of the nuclear phenomena. For staining the sections I used Heidenhain’s 
iron-alum-haematoxylin, either alone or in conjunction with Bismarck brown ; 
Flemming’s triple stain ; and gentian violet and orange G without safranin. 
As I obtained excellent results with the gentian violet and orange G 
without safranin, I used either this combination or the Heidenhain’s 
haematoxylin method for the majority of my preparations. 
Premeiotic Divisions. 
The resting nuclei of the archesporial cells of Equisetum arvense 
enclose a chromatic reticulum which varies somewhat in the degree of its 
fineness. In what are probably nuclei in a condition of complete rest this 
reticulum is very delicate and shows comparatively few and small chromatic 
aggregates. PI. LI, Fig. 1 gives a good idea of a nucleus in this condition. 
In other archesporial nuclei the reticulum is coarser and contains here and 
there somewhat more obvious chromatic aggregates. These small collections 
of chromatin most often occur singly upon the reticulum, but occasionally 
two such lumps may lie side by side. This paired arrangement of the 
chromatin bodies, where such occurs, is without doubt a chance phenomenon 
depending upon natural or artificial tensions in the nucleus which stretch 
