436 VEGETABLE PHYSIOLOGY 
the immediate neighbourhood of one another, so that. the 
transport of the antherozoids to other prothallia than 
their own is not at all difficult. After their liberation they 
are attracted to the archegonia by some constituent of the 
mucilaginous matter which is excreted from their necks 
when they open (fig. 181). In the Mosses this has been 
ascertained to be cane-sugar, in the Ferns it is malic acid 
or one of its salts. In the Rhodophycee and such Asco- 
mycetes as exhibit sexual reproduction, the passive male 
gamete, often called a spermatium instead of an anthero- 
Fic, 182.—DEVELOPMENT OF THE ARCHEGONIUM OF THE Fern. (After Kny.) 
zoid, is floated to the female organ or its trichogyne by 
currents in the water. 
In the Phanerogams, where the female gametophyte is 
always attached to the parent sporophyte, such a means 
of fertilisation is of course impossible. For fertilisation to 
take place it is necessary that the two gametophytes shall 
be produced in close propinquity to each other. This is 
effected by the bringing together of the two spores con- 
cerned in developing them. The microspore or pollen 
grain is carried by various means to the neighbourhood of 
the megasporangium; in the Gymnosperms it falls upon 
the megasporangium itself ; in the Angiosperms upon the 
stigma of the pistil in which the megasporangia are hidden. 
When it germinates the prothallium or gametophyte takes 
