ALG.E. 267 



wholly free from the parent plant before the contact of 

 the minute motile antherozoids which renders them 

 capable of immediate independent growth. They have 

 no provision for asexual multiplication by means of zoo- 

 spores. The Red Sea-weeds are multiplied asexually by 

 immotile spores and sexually, with varying degrees of 

 complexity in the apparatus, by means of germ-cells 

 which are fertilized by motionless corpuscles liberated 

 from the antheridia through the intervention of more or 

 less elongated slender tubular style -like prolongations 

 either directly or indirectly associated with the future 

 germ-cells. 



For further details of the structure of the Algae, I 

 must refer to the careful summary in Goebel's " Outlines," 

 and, for descriptions and figures of the marine species, 

 to the excellent works of the late Professor Harvey. 



Many species are used fcr food, and Fucus used to be 

 burnt for the sake of its alkaline ash (kelp) and for the 

 iodine which it contains. 



7. Natural Order Lichenes. The Lichen Family. 



Lichens occur either as cruet-like or leafy expansions, 

 or in little branching shrubby tufts, usually coloured grey, 

 orange, or greenish yellow. They spread everywhere 

 over stones, brick-walls, the bark of trees, and even upon 

 the most exposed rocks of Alpine and Arctic regions, 

 forming the very outposts of vegetation, and growing at 

 the expense, almost solely, of the atmosphere and the 

 moisture which it bears to them. 



Lichens are long-lived and intermittent in their 

 growth, being at a standstill and often easily crumbling 

 away when the weather is dry. A transverse section 

 through the crust (thallus) of a typical Lichen exhibits 

 under a magnifying power of 400 or 500 diameters imme- 

 diately underneath the upper cortical layer of rather 

 thick-walled cells, a stratum largely made up of green 

 chlorophyll-containing rounded cells, either scattered 

 singly or more usually clustered or joined end to end ; 

 these, under the name of "gonidia" have been hitherto 

 regarded as affording a means of vegetative propagation, 

 of the Lichen, the green cells, still retaining their vitality 



