294 Welsford.—Nuclear Migrations in Phragmidium violaceum . 
Falcariae (6), Endopkyllum sempervivum (11), Melampsora Linii (8), Puccinia 
Claytomata ( 9 ), Uromyces Caladii (3 and 9 ), Puccinia violae (9), Puccinia 
angustata ( 9 ), and Puccinia fusca ( 14 ). So far fertilization in the Uredineae 
by means of a migrating nucleus has been clearly observed only in Phrag¬ 
midium violaceum (1), and with somewhat less clearness in Uromyces Poae (2) 
and Puccinia Poarum (2). 
The far more common occurrence of the method of fertilization by the 
union of similar cells has led to some doubt being thrown on the importance 
of nuclear migration in the sexual process of this group. Olive ( 13 ) found 
nuclear migrations in Triphragmium Ulmariae and Caeoma nitens , but held 
them to be early stages of cell fusions, whilst Christman and Kurssanow, on 
the other hand, considered them to be pathological phenomena. Professor 
Blackman accordingly suggested to me the re-examination of the developing 
aecidium of Phragmidium violaceum , especially with a view to ascertain 
if cell fusions, as well as nuclear migrations, were to be found there. 
The material was collected on Leith Hill and in the neighbourhood of 
Guildford in the spring of 1913 and 1914. Owing to the difficulty of dis¬ 
tinguishing between Phragmidium Rubi and Phragmidium violaceum in 
the aecidial stage, teleutospores were gathered in the autumn from those 
blackberry bushes which had previously furnished the material of aecidia. 
The characters of the teleutospore were those of Phragmidium violaceum , 
Wint., the form investigated by Blackman ( 1 ). 
Special attention was paid to fixation in view of Christman's suggestion 
that the nuclear migrations might have been the result of wounding during 
that process. The young aecidial patches are red in colour and were always 
cut with a sharp pair of scissors from leaves still on the plant, leaving 
a margin of green tissue round each infected area. The material was then 
put direct into the fixative. Flemming’s strong solution, diluted with an 
equal quantity of water, was commonly used, penetration of the fluid being 
facilitated by the use of a small air-pump, so that the material sank in 
a few moments. Well-Axed material was also obtained by using in the same 
way Bouin’s picro-formol. As a control, some satisfactory preparations were 
made by momentarily immersing the material in 30 per cent, alcohol before 
placing in the Axing fluid ; this ensured the quick penetration of the fluid 
without the use of a pump. Material was also Axed in acetic alcohol. 1 
A very careful and prolonged search has been made for any indications 
of fusions between fertile cells of the young aecidium, but without success ; no 
case of this type of fertilization was found. Migrations of nuclei, such as were 
previously described by Blackman, occur regularly. The nucleus invariably 
passes from a vegetative to a fertile cell; sometimes the cells concerned 
belong to the same hypha and the nucleus passes from below upwards 
(PI. XVI, Fig. 9), and at other times the nucleus comes from a neighbouring 
1 Nuclear migrations were found*in material fixed in all these various ways. 
