262 
J. Ramsbottom, 
cell also divides. The septum between the trichophoric cell and the car- 
pogonium now temporarily dissappears and one of the daughter nuclei 
passes into the carpogonium. After this, a septum reappears. The pair of 
nuclei present in the carpogenic cell now undergo division and a trans¬ 
verse wall is formed which separates off a binucleate ascogonium from a 
binucleate supporting cell. Presumably the nuclei in the ascogonium 
again divide to provide the nuclei for a binucleate secondary inferior 
supporting cell which is sometimes cut off from the lower end of the 
ascogonium. The binucleate ascogonium may at once begin to bud 
off asci but it usually first divides by a nearly vertical wall into a 
pair of binucleate ascogenic cells. The nuclei of the ascogenic cells divide 
conjugately and mitotically. A daughter of each nucleus passes into the 
young ascus and a fusion takes place between them. The fusion nucleus 
unters upon a long period of growht finally undergoing three successive 
mitoses. „The first exhibits cleerly the phenomena said to be characteristic 
of meiosis, except that neither here nor in the two subsequent divisions 
is there any change in the number of chromosomes.“ Spore formation 
occurs in the same manner as in the ordinary Ascomycetes. Speaking of 
the Laboulbeniaceae as a whole, Faull finds that the cells of the thallus 
are typically uninucleate and that the nuclei divide mitotically. The 
spermatia are uninucleate in all the forms studied. Spermatia have been 
seen attached to trichogynes but their entrance into, or fusion with them 
has not been detected. Neither has the spermatium nucleus been detected 
migrating down the trichophoric cell although the carpogonium in every 
case studied became binucleate as also did later the ascogenic cells. No 
evidence of a nuclear fusion in the carpogenic cell or in the ascogonium 
has been seen, “though the possibility of the occurrence of such a fusion 
is not precluded”. Faull points out that the phenomenon of conjugate 
nuclear division, and the presence in L. chaetophora, of a reduced type 
of sexuality, suggest similar phenomena in the rusts and in certain As¬ 
comycetes. Also the “uninucleate antheridium, the possibility of prolife¬ 
ration of spermatia from the same antheridium, and the exogenous type 
of spermatium organisation, suggest similar phenomena in the rusts, many 
Ascomycetes and the Florideae ”. It seems rather unfortunate in many 
ways that a form which is lacking in spermatia should have first been 
chosen for cytological investigation instead of one of those forms in which 
Thaxter states that he has observed spermatia fused with the tricho¬ 
gynes. When such forms have been studied it will be possible to see 
whether the nuclear occurrences in L. chaeto'phora are normal or not, and 
whether the nucleus which migrates from the trichophoric cell into the 
carpogonium is to be regarded as a vegetative nucleus and thus com¬ 
parable with the migrating nucleus described in Phragmidium violaceum. 
In the Uredineae the nuclear phenomena seem now to be fairly 
well known but it seems extremely probable that there is much more 
variation in this group than was at first thought likely. By the work of 
various investigators, especially of Sappin-Trouffy, it was clearly shown 
that in the majority of cases, there is an alternation of a binucleate con¬ 
dition with a uninucleate one. The binucleate condition arises at the 
base of the aecidium. The two nuclei divide conjugately and the vege¬ 
tative and reproductive cells in the life cycle up to the mature teleuto- 
spore stage are binucleate. In the mature teleutospore the two nuclei 
