CYC AS RUMPim. 
193 
mucilage (muc.). This pollen grain is an abortive one, and 
hasJost its contents. On the left side of the pollen chamber 
are four male gametophytes (m.g.) that have grown normally 
and produced a pollen tube that has penetrated the nucellus. 
There is no definite orientation in the direction followed by 
the pollen tubes, except that they never seem to push their 
way through the base towards the archegonial chamber. 
This may be due to the fact that Cycas itself is not fertilized 
by means of a pollen tube, but by swimming ciliated gametes 
which pass through the broken base of the nucellar cap into 
the archegonial chamber. The stimulus directing the germi- 
nating pollen grain is then more or less lateral ; and the pollen 
tube growing into the nucellus acts then chiefly as an absorbing 
organ ; and this holds good even when the genus Cycas is 
pollinated either by Encephalartos or Macrozamia. 
Fig. 5 represents a detailed view of a fairly advanced 
condition of a male gametophyte. The ovule under examina- 
tion was about four months old, judging from its size. The 
diagram explains itself : v.c. is the vegetative cell, st.c. the stalk 
cell, p.t. the pollen tube ; m.c. is the mother cell, also called 
the body cell, and contains a large nucleus which will give 
rise to two male gametes ; the two blepharoplasts (hi.) have 
already taken their definite orientation prior to the formation 
of the two male gametes. One feature of the male game- 
tophyte is the great thickness of its outer cell-wall. From 
lack of sufficient literature ready at hand it is difficult to 
determine from the structure itself the genus to which the 
male gametophyte belongs. But it is clear enough it does 
not belong to the genus Cycas, and from personal observation 
and frequent visits to Peradeniya Gardens, I must refer this 
gametophyte either to the genus Encephalartos or to the genus 
Macrozamia. 
It is the writer’s hope to proceed further in his investigations 
and to establish more definitely some minor points that are 
still hypothetical. Meanwhile we may sum up the results 
obtained. 
Summary. 
1 . While female plants of Cycas Rumpliii are very abundant 
in Ceylon, no male plant has been observed of late years. 
