274 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Chloropliycete is undoubtedly occupied by forms, like the QEdogonieje 

 and Coleocbfeteas, in which the reproduction is definitely oogamous. 

 Two families of green algae present special difficulties in their 

 localizing under this arrangement, viz. Vaucheria, which, while having 

 itself highly diiferentiated sexual organs, is nevertheless nearly allied, 

 by its monosiphonous thallus, with the isogamous Siphoneae ; and the 

 Conjugatai. 



2. Phceophijcece ; corresponding nearly to Harvey's Melanosperme^e, 

 and including the Fucaceas, Cutleriaceae, and Thuret's Phaeosporeae 

 and Tilopterideas. This group has its lowest forms in the isogamous 

 Phaeosporeae, and its highest in the oogamous Fucaceae. 



3. BliodophycecB, comprising the Florideas, Porj^hyrefe, Bangieae, 

 and the marine Chantransieae, a well-defined group, with the 

 Dictyoteas as a doubtful member. 



4. (Jr7ji)tophycece (of Thuret) ; i. e. the Nostocaceae in the widest 

 sense of the term, including the Chroococcaceae and the Schizomycetes. 



5. Diatomacece. 



6. Characece. 



7. Fungi ; comprising all the organisms generally imderstood by 

 this term except the Schizomycetes and Myxomycetes, but including 

 the Lichens. 



8. Myxomycetes. 



If we turn our attention especially to the four largest of these 

 classes, the Chlorophycege, Phaeophycese, Ehodophycese, and Fungi, 

 we shall see that each constitutes a series complete in itself, ascending 

 from very lowly to higher forms, and that none of them dovetail into 

 one another ; although the lowest forms might in some cases be classed 

 indifferently in one or the other series. Thus Pytkium and the 

 simplest Phycomyceae, constituting the lowest member of the Fungi, 

 are closely allied to the Chlorophycefe. The series of Chlorophyceas 

 is connected upwards from the CEdogonieae and Coleochaetete, 

 through the Bryophyta, with Vascular Cryptogams and flowering 

 plants. The other three series do not lead up to higher forms. 



The simplest Phaeophyceae, as Ectocarpus, are separated from the 

 ChlorophyceaG by the structure of the zoospores, the formation of 

 phycoxauthin, &c., although exhibiting a distinct affinity with certain 

 chlorosporous forms, as Stigeoclonium, Chroolepus, and Cladophora. 

 The simplest Ehodophycefe, as Bangia, Chantransia, and Nemalion, 

 are already endowed with highly differentiated sexual organs, 

 and show most analogy to Cutleria and perhaps Tilopteris among 

 the Phaeophycefe, and to Coleochcete among the Chlorophyceas. 

 The Fungi, which find their highest development in the Ascomycetes 

 and UredineaD, show the closest relationship to the CEdogonieae 

 among the Chlorophyceae, MonohlepJiaris finding a place equally well 

 in this family or in the Phycomycetes ; and Pythium being also 

 almost equally well placed in the Chlorophyceae ; while Mycuidea 

 parasitica appears to be a chlorophyll-green, zoospore-forming 

 Peronospora. 



The anomalous Characeas present the appearance of being the 

 terminal member of a series of which the lower stages have been lost ; 



