Further Studies on the Cytology of the Ascus. 
BY 
H. C. I. FRASER, D.Sc. (Lond.), F.L.S. 
Head of the Department of Botany, Birkbeck College , London ; 
AND 
W. E. St. JOHN BROOKS, B.A. 
Assistant, Department of Botany, British Museum. 
With Plates XXXIX and XL, and a Figure in the Text. 
R ECENT investigations (8, 9 ) have shown that the three nuclear 
divisions in the ascus comprise two processes . of chromosome 
reduction. Such a state of affairs is necessarily correlated with the occur- 
rence of two nuclear fusions, and it has therefore seemed to us worth while 
to study the ascus divisions in forms in which fusion had already been 
reported in both the ascogonium and ascus. 
For this purpose Humaria granulata , Quel., Ascobolus furfur aceus , 
Pers., and Lachnea ster corea, Pers., were selected ; in each of these reduced 
fertilization has been observed in the ascogonium, and in each a second and 
subsequent fusion takes place in the ascus. 
Methods. 
The apothecia were fixed in various strengths of Flemming’s and 
of Hermanns fluid and were embedded in the usual way. Sections were 
stained with Flemming’s triple stain or with the iron haematoxylin of 
Heidenhain. In the latter case material was counter-stained with saturated 
solution of erythrosin in clove oil, or with Licht Griin similarly prepared. 
The latter substance, though unsatisfactory in aqueous solution, forms 
a very delicate cellulose stain when dissolved in clove oil ; in phanerogamic 
material it differentiates the cell-wall, leaving the middle lamella unstained. 
We are indebted to the Government Grant Committee of the Royal 
Society for the use of a Zeiss i mm. 1-40 apochromatic oil-immersion 
objective, a Swift panaplanatic condenser, and various other lenses. 
[Annals of Botany, Vol. XXIII. No. XCII. October, 1909.] 
