286 



PLANT LIFE. 



sperm. It is almost always ovoid or globular. The small 

 amount of body protoplasm of the sperm may be looked upon 

 as merely accessory. That of the egg, however, is usually 

 abundant and well supplied with reserve food, and it takes 

 part after fertilization in the formation of the new planL 



388. The ovary. — The organ in which the egg isproauced 

 is the ovary (oogonium, carpogonium, or archegonium). 

 Usually but one egg is produced in each ovary, though as 

 many as eight are formed in the Fucacese 

 (fig. 327). The ovary is either simple 

 or compound. 



389. A simple ovary consists of a 

 single cell, the bulk of whose proto- 

 plasm becomes one egg (or several). 



Fig. 324. 



Fig. 325. 



Fig. 324. — Egg of Fucus as it floats in sea-water, surrounded by many sperms, one of 

 which eventually plunges into it, unites with its nucleus and so fertilizes it. Magnified 

 350 diam. — After Thuret. 



Fig. 325. — Portion of two ovaries of an alga {Sfihceroplea annulina). The upper part 

 contains two eggs, and a number of sperms which have entered through the pore at 

 the side. The lower egg of the two shows the receptive spot above. A sperm is 

 partially imbedded in the protoplasm of this part in process of fertilization. The 

 egg in the lower ovary has been fertilized and has secreted a thick wall, thus becom- 

 ing a resting spore. Magnified 500 diam. — After Cohn. 



A portion of the protoplasm of the ovary is almost invariably 

 excluded from the egg (£, fig. 308). The sperms reach the 

 egg either through an opening formed in the wall of the 

 ovary (D, fig. 308, 325), or through a tube formed by the 

 spermary, which penetrates the ovary (fig. 307). 



