NOTES 
FERTILIZATION IN SPHAEROTHECA. — In connexion with a course 
of lectures on the Ascomycetes given by one of us, material of the Hop-Mildew 
(i Sphaerotheca Hwnuli , Burr.) was collected in the summer of 1904 for the purpose of 
following the development of the perithecium. As the results obtained, incomplete 
as they are, confirm the work of Harper 1 on the same object, it seemed worth 
while to put them on record, since the accuracy of his observations has been so 
directly called in question by Dangeard 2 , and also doubted by other workers (Lindau 
Holtermann, Kuyper). 
Fig. 17, 1 shows the oogonium and the antheridial hypha side by side; the actual 
antheridial cell has not yet been cut off. In Fig. 17, 2 (in which the plane of section 
is at right angles to that of Fig. 17, 1, and the antheridium is behind) there is actual 
cytoplasmic continuity between oogonium and antheridial cell, and the male nucleus 
has obviously just passed in ; the contents of both nuclei are somewhat contracted 
away from the nuclear wall. Four cases were observed in which the oogonium and 
antheridium were in open communication. In Fig. 17, 3 the two nuclei probably 
represent the sexual nuclei, as, judged by the branch which has only just begun 
to grow up from the basal cell, the stage is still quite young; it is, of course, 
possible that the two nuclei have been produced by division (as in Fig. 17, 6), for 
the development of the sheath, as some of the figures show, does not always 
run pari passu with the internal development of the oogonium. In Fig. 17, 4 the 
two nuclei which are in contact must clearly be the sexual nuclei just before 
fusion ; the nuclei here, also, are badly fixed, so that they stain in a homogeneous 
manner. Neither in this nor in Fig. 17, 3 is the communication between antheridium 
and oogonium now visible. In Fig. 17 , 5 the large single nucleus in the oogonium 
(oospore) represents, no doubt, the fusion nucleus. The non-nucleate antheridial 
cell is clearly visible here as well as in Fig. 17, 3, and in both these figures the separate 
origin of the hyphae which bear the oogonium and antheridium, respectively, 
is well seen. Fig. 17, 6 shows what are doubtless the first two nuclei formed by 
division in the fertilized oogonium ; the antheridial hypha, with the cell above 
containing only cytoplasm, is clearly visible on the left, having been pushed aside 
by the upgrowths from the basal cell which form the sheath. In Fig. 17, 7, a section 
from an older perithecium, is seen a row of four cells developed from the fertilized 
oogonium; the penultimate cell is binucleate and is the young ascus. 
We observed no cases in which the antheridial cell was without a nucleus 
while the oogonium was still unfertilized, nor any in which the antheridial cell 
still contained a nucleus when the oogonium showed two nuclei; neither did 
1 Ber. d. Deutschen Botan. Ges., xiii. 1895, p. [67]. 
2 Le Botaniste, 5 e serie, 1896, p. 245. 
[Annals of Botany, Vol. XIX. No. LXXVI. October, 1905.] 
