556 



HUTCHINSON'S POPULAR BOTANY 



The walls of the oogone consist of long twisted cells, the whole sur- 

 mounted by a crown of five or ten smaller cells, which ultimately separate 

 and form a neck with a central cavity leading to the interior. Here 

 there is a large central germ-cell (oosphere) with a receptive spot at its 

 apex, which becomes liquefied and so allows entrance to the antherozoids 

 when they have passed the narrow passage of the neck. After fertilization 

 the outer coats of the oosperm harden into a black pericarp, and later 

 the entire fruit falls off the plant to the bottom of the pond, where it 

 remains inactive till the following spring, when germination takes place. 

 At this period the oosperm has divided into one large and two small 



cells, the first apparently 

 serving as a reserve of 

 nutriment, whilst from 

 one of the smaller cells 

 a primary root is de- 

 veloped, and from the 

 other the proembryo a 

 long filament composed 

 of a single row of cells. 

 Across this a primary 

 node is formed, from 

 which arises a whorl of 

 rhizoids, and beyond the 

 node a very long inter- 

 node ; then another node, 

 from which arises a cluster 

 of leaves, amid which a 

 bud is formed, and from 

 this the new plant takes 

 its origin. The proem- 

 bryo is continued to a 

 great length beyond the 

 second node. It will be 



seen that in the entire life-cycle of the Characese there is no sporophyte, 

 so there is no true alternation of generations. 



We now reach the huge assemblage of forms that were until recently 

 grouped together under the general name of Algse, but are now separated 

 into a number of distinct Classes. Many of the species are familiar, as 

 common Seaweeds and plants of fresh-water ponds and streams. As in 

 the case of the Fungi, we can here only give a very brief indication of 

 the characters of each class. 



The RHODOPHYCE.E, or Red Seaweeds, sometimes termed Floridese, get 

 their name from the fact that in most of the species the chlorophyll in 

 the cells is masked by a red pigment known as phyco-erythrin. They are 



Photo by] 



FIG. 703. LIME-SECRETING PLANTS. 



\_E. Step 



The base of this group is a limpet whose shell has been thickly encrusted by 

 the strong seaweed Lithothamnium, from which grows a plant of Corallina. 



