STEIL: SOME NEW CASES OF APOGAMY IN FERNS 101 
the leaf always appears first, then that of the root, and finally that 
of the stem. A foot has never been observed to develop in any 
of the species in which the embryos were studied from prepared 
slides. Usually the leaf is much in advance of the root (PLATE 4, 
FIG. 9). A leaf, however, may be just making its appearance after 
the root has grown considerably in length (PLATE 4, FIG. 8). 
Both root and leaf, in the large majority of cases, are produced on 
the ventral side of the prothallium (PLATE 4, FIG. 7). PLATE 4, 
FIG. 12, represents a prothallium with an apogamous embryo the 
leaves and roots of which are ventral. Either root or leaf or both 
may appear on the dorsal surface (PLATE 4, FIGS. 10 and 11, and 
PLATE 5, FIG. 16). In the cultures of Aspidium chrysolobum and 
A. hirtipes embryos of this nature have been observed. Such 
anomalies may be produced by light conditions as Leitgeb (1885) 
has shown. 
As a result of studies thus far made, it has not been determined 
whether the apogamous embryo owes its origin to a single super- 
ficial cell or to inner and outer cells of the prothallium. 
Frequently, in some of the cultures, more than one embryo was 
observed to develop from a single prothallium. This was espe- 
cially the case when the prothallia showed a tendency to become 
lobed (PLATE 4, FIGS. 3 and 4). PLATE 4, FIG. 3, represents a 
prothallium of Pteris cretica albo-lineata Alexander with a young 
embryo posterior to the apical region, and tracheids in each of 
the two secondary regions of growth. Another prothallium of 
the same variety is shown in PLATE 4, FIG. 4. In this instance 
tracheids are present in the apical region, and two embryos have 
been produced on other portions of the prothallium. One of these 
is produced in the apical region of one of the main lobes, and the 
other is a vegetative growth on the inner margin of a lobe itself. 
Each of these embryos has produced a small leaf, J, and a root, r. 
The embryos in such cases, as is readily seen, are wholly independ- 
ent of one another. In some instances it was observed that some 
of the tracheids extended from the apical notch of the prothallium 
to one or both of the inner margins of the lobes where the embryo 
was produced (PLATE 5, FIG. 19). It may be stated in this con- 
nection that embryos are not always produced when tracheids are — 
formed, but in most cases these tissue-elements indicate the be- 
ginning of an apogamous embryo. 
