440 



REPRODUCTION. 



1136. 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 obsphere, 

 is fertilized by specialized threads or slender masses of protoplasmic matter 



termed antherozoids, coming 

 from another part of the 

 same or of another plant. 

 By contact with these an- 

 therozoids the oosphere be- 

 comes an obspore, the start- 

 ing-point of a new individual. 

 In this group, of which 

 Fucus or rock -weed may lie 

 taken as an example, the 

 fertilization is direct. 



In 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 

 f "jgf*i frond, and in a vertical di- 



c\ Nix' -/ HHU rection. Good preparations 



can be obtained from mate- 

 rial which has been dried or 

 from that which has been 

 kept in alcohol, and winter specimens will be found esj)ecially good. 



Some of the species are 

 dioscious, having the male 

 elements in the conceptacles 

 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 

 PIG. 210. Fucus, illustrating the fertilization of an oophyte. 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 (</); e, an oosphere 

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



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

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

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



