1912] REY NOLDS—PARASITIZED LEAF TISSUE 383 
Discussion and conclusions 
The changes which are caused in leaf tissue by parasitic fungi 
are similar to those which have previously been reported as 
occurring in other parts of phanerogamic plants, and caused by 
insect invasion, changes of temperature, and parasitic fungi. A 
comparison of the observations reported in the latter part of this 
paper with those of other workers reviewed in the earlier part will 
show that the enlarging, changing of form, and dividing of the 
nucleus, the changing of the composition of the cell walls, the 
reduction in the amount of chlorophyll, and other changes in the 
normal content of the leaf cells are all duplicated in other organs 
affected by destructive agents. 
These changes are usually only variations of natural processes, 
and are not phenomena that are known only in pathologic tissues, 
for it is to be noted that these changes in the appearance of the 
nuclei are not unknown in normal vegetable cells. JoHow (33) 
describes amitosis as occurring in the older cells of Chara foetida. 
The presence of two or more nuclei in a cell has been noted by 
TREUB (78) in bast cells of various plants; while a process of division 
is reported by VON BRETFELD (8) and MAssart (42a) as so common 
in wound tissues that they believed nearly all such tissue is formed 
by the “‘amitotic’’ process, as they called it. More detailed work 
is necessary to show whether the amitotic process of Jonow and 
the processes of nuclear division in wound and disease tissues are 
really analogous, since the former process seems to be for the 
purpose of increasing the nuclei in connection with the metabolism 
of mature cells, and the latter processes often lead to an increase in 
the number of cells, and are found in cells apparently stimulated to 
a kind of rejuvenescence. ScuiiRHOFF (67), moreover, has shown 
that this idea is far from correct, since there are many cases of 
mitosis in wound tissue, and no true amitosis is certainly known in 
these tissues. A process that appears to be true amitosis has 
been reported by SHIBATA (68) in mycorhizal cells, and by TIsCHLER 
(76) in Heterodera galls on Circaea. A rather detailed discussion of 
this question is given by Miss DALE (15); while Ktsrer (40) and 
STRASBURGER ('74b) review the whole subject of the direct and 
indirect methods of nuclear division. 
