448 VEGETABLE PHYSIOLOGY 



CHAPTEE 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 as 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 megaspo- 

 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 



