Some Problems of Reproduction: a Comparative Study of ...

SOME PROBLEMS OF REPRODUCTION. 29
the zygotes emits a tube^which may abstrict spores or grow
into a vegetative mycelium. This germination of the gametes
may in some cases take place facultatively independently of
conjugation. 1
PROTOMYCES resembles Ustilaginese in the behaviour of its
gametes; but they are formed endogenously in large numbers
in the spore, leaving a quantity of non-nucleated epiplasm.
In UREDINEJE Massee has described a process of siphonogamous
2 Conjugation between a larger "oogonium" and a
smaller antheridium comparable to that of the lower Ascomycetes*
The only cytological observations of importance
given are that the oogonium is uninucleate before fertilisation,
and contains several small nuclei on the third day.
C. HIGHER THALLOPHYTES.
1. Floridese.
The Red Seaweeds stand apart from the other Thallophytes
in many respects, and we follow Falkenberg 3 in regarding
them as distinct from the true Algse. Their male reproductive
cells or "spermatia" are all but motionless, and scattered
by local currents. Their female cells, " carpogonia" or
" procarpia," are usually permanently fixed in the thallus.
They emit a trichogyne which does not open, and is abstricted
after receiving the male pronucleus by conjugation
with the spermatium, and transmitting it to the female pronucleus
in the base of the " carpogonium."
1
It is noteworthy that the formation of gametes here takes place at a stage
in no way homologous with the sexual organs of the (more primitive) Ascomycetes.
It would seem, indeed, probable that this gametal process has
originated de novoasa specialisation of and advance upon the free anastomoses
formed between contiguous young hyphse in so many of the higher Pungi.
There is, indeed, no reason why such processes should not originate afresli at
a different stage in forms that have become apogamous by the complete loss
of a sexual process at the usual stage.
s
" On the Presence of Sexual Organs in iEcidium," iu ' Ann. of Bot.,'
vol. ii, 1888.
3
In his monograph of the Alg» in Schenk's ' Handbuch der Botanik.'