102 CLASSIFICATION OF THE MICRO-ORGANISM? . 



are divided into the stem-forming cryptogams, and the 

 thallophytes, or leafy plants, in which only a leaf or 

 ihallus is formed, which does not in any way follow the 

 laws of growth of the higher stem-forming plants. 

 Former sub- The thallophytes w r ere formerly divided into three 

 SjjjfSJjJ" sub-classesfungi, algae, and lichens. The fungi 

 and lichens, were defined as cells devoid of chlorophyll, which can 

 only obtain nutriment from previously formed organic 

 compounds, and hence can only live as saprophytes on 

 organic substances undergoing decomposition, or as para- 

 sites in living plants and animals. Alga? were described 

 as cells always containing chlorophyll, which obtained 

 nutriment from inorganic materials, and for the most part 

 lived in water. Lichens were defined as a mixture of 

 cells, some containing chlorophyll and others without it, 

 which could obtain nutriment from inorganic materials, 

 and for the most part lived in the air. 



Untenabiiity At the present time very little value is attached to 

 catk)n. elaSSifi " tliese distinctions, which are based chiefly on the pre- 

 sence or absence of chlorophyll. Even among the 

 phanerogams there are many plants which are devoid 

 of chlorophyll (orchids, monotropaceae), but which are 

 not on that account struck out of the families or orders 

 to which from their morphological characters they 

 belong. If also in the case of the thallophytes the chief 

 stress is laid on the mode of propagation, and on the 

 morphological characters, the fungi and algae show a 

 great deal that is common to both. And with regard 

 to the lichens the latest investigations have shown with 

 considerable certainty that they consist of a fungus and 

 an alga, the first of which preys upon the second, so that 

 they cannot be looked upon as an independent class. 

 Hence it is best to give up the former division into 

 fungi, algas, and lichens, and to choose for the whole 

 of the thallophytes a principle of classification in con- 

 formity with that employed for the other plants. 



Opinions vary greatly as to the most suitable and 

 natural mode of classifying the thallophytes, but we 

 need only refer here to de Bary's classification (Vcr- 

 fflcichende Morphologie und Biologic dcr Pilze, page 



