NUCLEAR STRUCTURE AND SPORE FORMATION IN 
MICROSPHAERA ALNI. 
M. C. SANDS. 
(With Plate XLVI.) 
INTRODUCTION. 
The literature on the development of the ascus and its cy¬ 
tology has been recently and fully reviewed (4, 13), and I 
shall refer only to such very recent papers as touch upon the 
points with which I have been specially concerned. 
Faull (5) describes for Hydnobolites , Neotiella , Sordaria 
and some other species, a method of spore formation which he 
considers ^essentially different 'from that described ’for ithle 
Aacomycetes by Harper (9, 11). He finds the central body 
by no moans a permanent feature of the cell. In Sordaria , 
certain of the resting nuclei show centers, but in the 
other species centers with asters appear only at the time of 
division, disappearing in resting stages. Faull believes that 
the spindles are strictly intranuclear in origin, the spindle 
poles being the centers from which the long astral rays extend. 
In the last division Faull finds the same persistence and sub¬ 
sequent bending of the astral rays as has often been described 
for spore formation, but attaches no importance to the rays or 
their activity as far as spore formation is concerned. 
The first indication of spore formation, according to Faull, 
is the appearance of a specialized layer of cytoplasm beginning 
just around the center and developing progressively outward 
and around the nucleus until it encloses the cytoplasm of the 
future spore. He compares this limiting layer to the hyaline 
zones found in the cleavage stages of the protospores of Pilot- 
