Graham. — Nuclear Division of Preissia com mu l at a. 667 
of the reticulum are at least in contact with the nucleolus. The actual 
connexion of the nucleolus with the reticulum and with the chromosomes 
has often been observed by other students, some of whom believe that it 
furnishes a portion of the substance 1 for the chromosomes. Wager (’04) 
says that in the vegetative cells of Phaseolus the nucleolus contributes 
a large part of its substance to the formation of the spireme and the chromo- 
somes. During this process the nucleolus undergoes changes of form, 
becoming amoeboid, then vacuolate, and finally spongy. After the chromo- 
somes were fully formed, the remainder of the nucleolus divided into 
unequal portions which moved towards the poles of the spindle. In 
Preissia commutata I have not observed the nucleolus after the dissolution 
of the nuclear membrane. At metaphase, of which there are many sections, 
all the chromatin is readily identified as chromosomes. A dividing nucleolus, 
such as Wager (’04) found in Phaseolus , and a dividing nucleolus and frag- 
mented portions of the nucleolus lying in the cytoplasm surrounding the 
spindle at metaphase, such as Thos. Martins Mano (’04) found in Phaseolus 
and Solatium, and as has been described by others, were not observed by 
me in the vegetative cells of Preissia commutata. When the spireme has 
segmented and the chromosomes begin to shorten and thicken (Figs. 13 , 14 ) 
the nucleolus is of the same size as it is in the earliest prophase. Nor has 
its surface appearance and staining capacity changed so far as I could 
observe. These facts lead me to believe that the nucleolus does not give 
up its substance to the formation of the chromosomes, or, at any rate, not to 
any appreciable extent. But the sudden disappearance of the nucleolus 
coincident with the formation of the central spindle suggests that its sub- 
stance may be transformed into spindle fibres. That the substance of the 
nucleolus is concerned with the formation of the spindle fibres is a view 
held by a number of students. Nemec (’99) studied mitosis in the Seed 
Plants and came to the conclusion that the nucleolus takes part in the 
formation of the spindle. He describes the reverse process, that is, the 
mantle fibres become granular and by consolidating form the nucleoli of 
the daughter nuclei. Strasburger (’05), who worked at both Monocotyledons 
and Dicotyledons, was convinced that the nucleolus contributes some sub- 
stance for the formation of spindle fibres. Miyake (’05) is in entire accord 
with Strasburger’s view. A number of Monocotyledons were investigated by 
Miyake, and he describes and figures fully formed chromosomes while the 
nucleolus still persists. Many others hold the same view. Chamberlain 
(’03), who studied the germinating spores of Pellia epiphylla , suggests that 
the substance of the nucleolus is used partly in the formation of the 
1 In the nth edition of Lehrbuch der Botanik (by Strasburger, Jost, Schenk, and Karsten), 
1911, in the section ‘ Morphology p. 73, Strasburger says that the nucleolus appears to represent 
reserve stuff which serves for the nourishment of the chromosomes and also furnishes some substance 
for the spindle threads. 
