Embryo of Botrychium obliquum , Miihl . 
147 
The Embryo. 
The embryo of B. obliquum differs remarkably from that of either 
B. Lunaria or B. virginianum. Lyon 1 called attention to the presence of 
a conspicuous suspensor and .a very different orientation of the cotyledon 
and root when compared with B. virginianum. He describes and figures 
the young sporophyte at about the time that the root emerges from the 
gametophyte, but he does not state just what is the relation of the organs of 
the young sporophyte to the early divisions of the embryo. 
Bower 2 has figured several unicellular embryos from Dr. Lyon’s 
preparations, showing the marked elongation of the embryo before the first 
cell division, but no later stages were found. 
B. obliquum was the first fern in which a suspensor was demonstrated, 
but subsequently the writer discovered a suspensor in two members of the 
Marattiaceae, Danaea 3 and Macroglossu m . 4 Helminthostachys has also 
been shown to possess a suspensor. 5 
The following account of the embryo of B. obliquum is based in part 
upon slides made by Dr. Lyon, and partly upon preparations made by the 
writer from prothallia and young sporophytes collected by Dr. Lyon. 
Unicellular embryos are not uncommon, as several archegonia may be 
fertilized, and begin to form embryos ; but the later stages are not so easily 
found, and it was not possible to secure as complete a series as might have 
been wished. However, the essential points in the development of the 
embryo were made out, and there is no question as to the way in which 
the young sporophyte develops. 
As usual, the fertilized egg immediately forms a cell-wall, and grows 
until it completely fills the cavity of the venter. The unicellular embryo is 
at first globular in form, and contains only *a small amount of granular 
cytoplasm in which is embedded the relatively small nucleus (Text-fig. 4, A). 
The lower part of the embryo next becomes slightly pointed, and this pro- 
jection contains most of the granular contents of the cell, and the nucleus, 
which has become somewhat larger. The embryo now grows downward, as 
Bower has shown, and bores its way into the adjacent prothallial tissue. 
Sometimes it grows vertically downward, but more often its course is more 
or less oblique. At this stage it forms a somewhat irregular tube, whose 
apex is narrower than the basal portion within the venter of the arche- 
gonium. The nucleus and the surrounding granular cytoplasm, which has 
increased considerably in amount and shows a more or less evident areola- 
tion, occupy the growing apex of the embryo-tube, which may be three 
times as long as wide before the first cell division occurs (Text-fig. 5, a). 
1 Loc. cit. 
2 Bower, F. O. : Origin of a Land Flora, Fig. 266. 3 Campbell : loc. cit. 
4 Campbell: Ann. Bot., xxviii. 652, 1914. 5 Lang, W. H. : Ann. Bot., xxiv. 611, 1910. 
