128 
Berridge and Sanday. 
interesting specific differences are to he noted. A fuller account is 
given of the sequence of events in the later development of the 
ovule, and a comparison of this with the very divergent accounts 
given hy Strashurger and Jaccard seems to indicate that the 
different species of Ephedra may form a transitional series linking 
the isolated genera Gnetum and Wehvitschia with the more typically 
Gymnospermous families. The unusual character of the crnhryo- 
gcny in some cases seemed of sufficient interest, in the light of 
much recent work on both Gymnosperm and fern prothallia, to 
justify the publication of an account of it at once, though only an 
extended series of investigations can determine how far the 
apparently abnormal development is usual in the genus, or how far 
it is to he attributed to a somewhat cold and late season at the time 
of gathering the material. E.M.B. 
DEVELOPMENT OF THE OVULE. 
I.—The Embryo-Sac. 
The Kew material of Ephedra distachya furnished a series of 
stages in the development of the embryo-sac, commencing with the 
appearance of the unicellular megaspores, which agrees in nearly 
every particular with that of E. trifurca, as described by Dr. Land. 
The youngest ovule of the series, however, differs from Dr. 
Land’s examples in respect of the arrangement of the megaspores ; 
this appears to he tetrahedral, as shown in Fig. 1, and not linear, 
The third megaspore is evidently the functional one ; there appears 
to be a fourth, but it has already begun to degenerate, and is only 
partly seen in this section. Also in several cases of slightly older 
embryo-sacs containing a few nuclei, the remains of sister spores 
are found lying in oblique positions round them and not directly 
above, indicating that here also the arrangement has been tetra¬ 
hedral. The cells surrounding the megaspores, which become 
crushed and disorganized as the growth of the embryo-sac proceeds, 
are in no way differentiated to form a tapetum. 
At this period the integument is beginning to grow up; it arises 
earlier on the inner adaxial side of the ovule than on the outer, as 
is clearly evident in the section from which Fig. 2 is taken. Here 
the left-hand ovule, containing unicellular megaspores, is over-topped 
by the integument on the inner side, while abaxially only a slight 
swelling indicates its position. The right-hand ovule, containing a 
