SEXUALITY OF PLANTS 35 



of substances have been tried, and of various strengths. 

 It has been found that a solution of malic acid, of strength 

 about o-ooi p.c., diffusing out into water, serves as a 

 positive attraction, leading the spermatozoids to the 

 neck of the flask, which they actually enter as they 

 would a real archegonium. It is therefore concluded as 

 probable that a soluble substance, similar in its action 

 to malic acid, is given out from the ovum, and serves 

 to direct the movements of the spermatozoids. 



The deeply seated position of the ovum in a Fern is 

 clearly an advantage in the protection and nutrition of 

 the fertilized egg (Fig. 13). The maternal tissue closely 

 surrounds the embryo at first. A connection is kept up by 

 means of a suctorial "foot," between the embryo that grows 

 from the egg and the parent prothallus (Fig. 18) . This per- 

 sists until the young plant is established so as to be able 

 to nourish itself by its own root and leaf. On the other 

 hand we see that the position of the ovum at the base 

 of the flask-shaped archegonium offers no serious obstacle 

 to syngamy, provided the attraction of the motile sperma- 

 tozoid is as effective as experiment proves it to be. This 

 has been the method of sexual propagation of all the 

 primitive Plants of the Land. They are represented by 

 the Mosses, Ferns, Horsetails, and Club-Mosses. Such 

 Plants proclaim their aquatic origin by retaining the 

 ancestral method of syngamy through water. They are 

 not typical Plants of the Land, but might be properly 

 called the Amphibians of the Vegetable Kingdom. They 

 have, speaking figuratively, one foot on land and one 

 still in the water. They cannot complete the cycle of 

 their life in its most critical point, that of the sexual 

 production of a new individual, except when external 

 fluid water is present. Without it the spermatozoids 



