448 VEGETABLE PHYSIOLOGY 
CHAPTER XXVI 
REPRODUCTION (CONTINUED) 
We have seen that the phenomena of fertilisation are 
preceded in the Spermophytes by an arrangement through 
which the two gametophytes, which give rise respectively 
to the male and female sexual cells, are developed in such 
close proximity that they ultimately come into contact. 
That which is produced ag the result of the germination 
of the microspore, or pollen-grain, is a tube of varying length, 
which bores its way through the tissue of certain parts of 
the sporophyte, being guided in some manner not yet fully 
understood, until it reaches some part, usually the apex, 
of the megaspore or embryo-sac, in which synchronously 
the prothallium which bears the oosphere has been developed. 
In the process of sexual reproduction in these plants we 
have two phenomena presented, which have often been 
treated of as if they were inseparably connected. The 
first of these, which is known as pollination, involves merely 
the transport of the pollen-grain to an appropriate position 
on some part of the megasporophyll or of the megagspo- 
rangium itself. The second, which may or may not follow 
the former one, is the actual fusion of the gametes which are 
produced upon the gametophytes to which the spores give 
rise, and which therefore must be considerably later in the 
time of its occurrence. This is what we have already 
described as fertilisation. 
It is necessary to insist on the distinction between 
these two processes, as the phrase ‘the fertilisation of the 
