440 



REPRODUCTION. 



1 136. It was formerly thought that no clear gradations could 

 be detected between the flowering plants and the higher groups 



(3) Oophytes. In this group a mass of protoplasm, known as an oosphere, 

 is fertilized by specialized threads or slender masses of protoplasmic matter 



termed antherozoids, coming 

 from another part of the 

 same or of another plant. 



/^Wll B Y contact with these an- 



tl f erozoids the O5sphere be _ 



comes an oospore, the start- 

 ing-point of a new individual. 

 In this group, of which 

 Fucus or rock-weed may be 

 taken as an example, the 

 fertilization is direct. 



1 n the examination of this 

 group the student may em- 

 ploy the common rock-weed 

 which carpets the boulders 

 along the coast. Sections 

 should be made in the un- 

 even pustulated part of the 

 frond, and in a vertical di- 

 rection. Good preparations 

 can be obtained irorn mate- 

 rial which has been dried or 

 from that which has been 

 kept in alcohol, and winter specimens will be found especially good. 



Some of the species are 

 dioecious, having the male 

 elements in the conceptaclcs 

 on one plant and the female 

 elements in those upon an- 

 other. 



(4) Carpophytes. The 

 simplest plants of this het- 

 erogeneous group are illus- 

 trated by Fig. 211. The 

 oosphere is contained in a 

 specialized organ (the car- 

 pogonium), which is fre- 

 quently prolonged to form 

 a style-like process (the tri- 

 chogyne). The antherozoids 



are carried "by water to this process, and fertilization results ; the product of 



FIG. 210. Fucus, illustrating the fertilization of an obphyte. a, section through a 

 conceptacle exhibiting the reproductive organs; b and c, the oospheres in different 

 stages of development; d, antheridia with a single antherozoid (f/); c, an oosphere 

 surrounded by antherozoids; /, an oosphere germinating. (Thuret ) 



FIG. 211. Nemalion. I.-IV., a carpophyte. I., a branch showing antheridia, a, and 

 a carpogonium, o, with tlie trichogyne, f (e, spermatium). V., Lejolisia exhibiting a, an- 

 theridiinn, c, carpogonium, and/, ripe fruit; e, an escaping spore. (Thuret and Bornet.) 



210 



211 



