l8 99-] Johnson. — The Irish Characetz* i^j 



formed an antherozoid passes and on through the mucila- 

 ginous wall of the oogonium to the receptive spot in the egg- 

 cell. 



The antherozoid fuses with the nucleus of the egg-cell and 

 so fertilisation is completed. Food matter now accumulates 

 in the egg-cell ; the oospore and the involucre become 

 darker in colour and thick-walled to protect the oosperm 

 from injury during its period of rest — at the bottom of the 

 pond, etc. — from the autumn till the following spring when 

 germination takes place. The nucule 1 bursts open and two 

 little threads grow out ; one into the mud as a root, the other 

 is green, and on it a new plant arises in a way which need not 

 be described here. In addition to this sexual reproduction 

 vegetative propagation is not uncommon. Cells of the root- 

 filaments may become filled with starch, round off, and as 

 bulbils give rise to new plants. Starch-stars arise by some of 

 the surface cells of a node growing out and becoming filled 

 with starch. This is well seen in Tolypellopsis in which the 

 nucule rarely ripens. Other ways of simple reproduction are 

 also known. Chara cancsccns {crinita) is remarkable in that the 

 egg-cell gives rise to a new plant parthenogetically, i.e., 

 without fertilisation. C. crinita was discovered in Ireland in 

 1894 by Dr. R. W. Scully. 



Migula regards the Characeae as a group of plants indepen- 

 dent of the two subkingdoms of the Thallophyta, and the 

 Bryophyta (including Mosses and Liverworts) and proposes a 

 new subkingdom — the Charophyta — for their reception. Their 

 relationships are thus indicated : — 



Bryophyta. 



Charophyta. 



Coleochabte, 



Chlorophyceae. 



Thallophyta. 



1 By nucule one understands the resting oosperm with the more or 

 less complete involucre and corona //present still. 



A 2 



