THE COMMENCEMENT OF THE PHANEROGAMIC FRUIT. 71 



spermatoplasm is segmented up into many fragments; these escape from the 

 antheridium and reach the simple fruit-rudiment by swimming. Since the sper- 

 matozoids are attracted to the young fruits by certain excretions which the latter 

 pass out into the water, the multifarious devices associated with aerial fertiliz- 

 ation are unnecessary. Protective coats around the sexual organs, sheaths to limit 

 evaporation, brightly-coloured or sweet-smelling floral-leaves to attract insects that 

 they may transfer the pollen from flower to flower all these are wanting in 

 plants which are fertilized under water. Now it is just these accessory protecting 

 structures which constitute what are called blossoms. Thus we can say that 

 these water-plants have no blossoms. To avoid misconception it must be stated 

 that although they have no blossoms they have flowers. For although, popularly, 

 blossoms and flowers are used as synonymous terms, under flowers are compre- 

 hended the organs which are concerned in fertilization, under blossom merely the 

 leaves which inclose the essential organs and which guard and protect the young 

 fruits and stamens. It is these latter which produce the sexual protoplasts. 

 Their union is promoted by the leaves of the blossom. Sometimes they catch 

 the pollen-grains as they are blown by the wind, or by the production of honey 

 and scents attract insects which remove the pollen in their visits. In other 

 cases, by projecting ridges and corners, they are instrumental in detaching the 

 pollen from these same insects, and in a thousand ways protect and assist the 

 difficult process of aerial fertilization. 



In the above lines we have been speaking not of aquatic plants generally, 

 but of such as are fertilized under water. And these should be carefully distin- 

 guished. Many aquatics, which pass their lives under water, send up their 

 flowers to the surface so that their fertilization is aerial. On the other hand, 

 strange though it may seem, the fertilization of most aerial Lichens, Mosses, and 

 Ferns which grow on the sand of desolate moors, on the sunny rocks of mountain 

 sides, or on the dry bark of old tree stems, is accomplished under water. Plants 

 of this sort may be exposed to drought for many months, and the movement of 

 sap within them may be suspended; but when they are moistened with rain or 

 dew they are quickened and rejuvenated, and form their young fruits and 

 antheridia. Things are so arranged that the liberation of the spermatozoids 

 coincides with the moment at which these plants have access to sufficient 

 moisture. Thus we see that it is literally true of these plants whether growing 

 on the bough of a tree or in a ravine on a mountain side that their fertilization 

 is accomplished under water. 



The only really important distinction between plants permanently submerged 

 and such as are thus situated from time to time, is that in the latter the young 

 sexual organs are protected against desiccation during the periods of exposure by 

 means of sheathing structures and leaf -like scales, as is particularly well shown 

 by the Mosses. Blossoms in the usual sense, however, are not found amongst Ferns 

 and Mosses, and we can make the following three general statements: (1) That 

 Cryptogams are fertilized under water and most Phanerogams in the air; (2) that 



