Generations , and General Cytology of the Uredineae . 367 
violaceum and some other forms is without particular significance, and is 
apparently a mere precocious division in which wall-formation is delayed. 
The view which has been put forward, that the sporidium starts in the 
life-history the condition with paired nuclei, is without foundation, for in all 
cases observed the mycelium arising from the sporidium has single nuclei, 
even in such cases as Phrag. violaceum , where the sporidium is known to 
be usually binucleate. 
The teleutospore is really of the nature of a spore-mother-cell, the 
contents of which, usually after germination (but directly in Coleosporium ), 
break up by a tetrad division into a series of four primary spores (the 
so-called promycelial cells). These can separate and put out germ-tubes, 
and no doubt cause infection ; normally, however, when growing in free air, 
they remain connected and their germ-tubes become arrested, so that four 
secondary spores — the sporidia — are formed. The term promycelium is 
thus a misnomer. 
NOTE. 
It is obvious that the method of development of the fertile (female) cells in the 
aecidium of Phragmidium may be considered as a new type of so-called partheno- 
genesis ; for, just as in Artemia there is a fertilization of c parthenogenetic ’ eggs by 
the second polar body (nucleus) instead of by a spermatozoon, so in this case the 
nucleus of a vegetative cell has apparently replaced in function that of the spermatium. 
The term parthenogenesis is, however, an unsatisfactory one, as it is not very aptly 
applied to these cases in which there is a process of nuclear fusion ; it would be 
much more satisfactory to confine the term to cases in which the sexual cells actually 
develop with the reduced number of chromosomes, without any form of fertilization. 
There is the same difficulty with apogamy now that we know that in apogamous Ferns 
the nuclei of prothallial cells may fuse together, for the application of this term 
suggests a denial of the existence of any process of fusion of cells or nuclei which 
could be considered of the nature of gametic fusion. 
It becomes clear that cytological investigations of recent times have practically 
broken down the distinction between fertilization, parthenogenesis (in the wide, but 
not in the narrow, sense suggested above), and apogamy. Between the fusion of an 
egg-cell with a differentiated male cell, the fusion (association) of an egg-cell with 
a vegetative cell (or nucleus), the fusion of an egg-cell and its polar body, and the 
fusion of two vegetative cells (or nuclei) no sharp line can be drawn, and they must 
all be considered as terms in a series of fertilizations. Just as on one side of normal 
oogamous fertilization with its differentiated male and female cells there are such 
primitive types of fertilization as isogamy, and that, the most primitive, in which there 
is no distinction of sexual and vegetative cells ; so, on the other side, there is a series 
of reduced processes of gradually increasing simplicity, the most simple being 
practically a return to the most primitive, where the sexual and vegetative cells are 
alike. Apart from the presence of the functionless spermata and the peculiar 
migration of the nucleus through a cell-wall, which show that it is reduced in evolu- 
tion, there is nothing to clearly distinguish the process observed in Phragmidium 
from such accepted fertilizations as the conjugation of adjacent cells in a Spirogyra 
filament, the fusion of gametes (which are of the relationship of cousins) in 
Adinosphaerium , or from such a process as is to be observed in Basidiobolus, or 
even other Fungi, in which the sexual organs arise on neighbouring cells of a hypha. 
