440 



EEPRO0UCTIOK. 



113G. It was formerh- 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. 

 By contact with these an- 

 therozoids the oosphere he- 

 comes an oospore, the start- 

 ing-point of a newindividuah 

 In this group, of which 

 Fucus or rock-weed may he 

 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 tlie coast. Sections 

 should be made in the un- 

 even pustulated part of the 

 frond, aud in a vertical di- 

 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 especially good. 



Some of the species are 

 dioicious, having the male 



elements in the conceptacles » /It^fisH '^ 



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- 

 cKogyne). The antherozoids ^1^ 



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

 Fig. 210. Fucua, illustrating the fertilization of an oophyte. a, section throngli a 

 conceptaclo exhibiting the reproductive organs; b anil c, the obspheres in different 

 stages of development; d, antheridia with a single antherozoid ((/); e, an oSsphere 

 surrounded by antherozoids; ./•, an oosphere gei-niinaling. (Thuret ) 



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

 a rarpogonium, o, with the triohogyne, t (e, spemiatium). V., Lejolisia exhibiting a, an- 

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



210 



