GENERAL MORPHOLOGY. 103 



142), to Brefeld's subdivision (Untersuchungen ilber 

 Schimmelpilze, Heft 4), and to Frank's classification 

 in the third edition of Leunis's Botany, page 398. The 

 present description will be based chiefly on Frank's 

 classification, because Leunis's Synopsis is an indis- 

 pensable book of reference for anyone who studies the 

 thallophytes minutely. 



Among the thallophytes only the fungi are at present 

 of hygienic interest, hence the algae and lichens are not 

 at all referred to in the following pages, and with regard 

 to the forms of algae, morphologically similar to the 

 fungi, reference must be made to Leunis's Synopsis and 

 to Colm's Beitrage zur Biologic der Pflanzen, Bd. 1, 

 H. 2. 



From the hygienic standpoint it seems most practical Subdivision of 

 to depart from the botanical arrangement and divide a practical* 01 

 the fungi into four chief groups, of which the first 

 comprises the true fungi, or mould fungi ; the second the 

 mycetozoa ; the third the yeast fungi, or blastomycetes ; 

 and the fourth the fission fungi, or schizomycetes. 



I. THE FUNGI PROPER (MOULD FUNGI). 



General Morphology. 



The fungi consist of small microscopical cells, in Nature of the 

 which we can distinguish a membrane and protoplasmic fun u * 

 contents. The cell membrane is composed of a sub- 

 stance similar to cellulose but not identical with it, 

 and does not show any violet colouration with iodine. 

 In the protoplasm there are as a rule no nuclei, no 

 starch granules, and no chlorophyll ; on the other hand 

 there are frequently vacuoles, oil globules, various 

 colouring materials, and at times crystals of oxalate of 

 lime which are however deposited especially on the 

 outer surface of the cell wall in the form of small 

 needles and prickles. 



The growth of the fungi takes place by elongation of Hypha>. 

 the cells. Thus a series of threads or hyphae are 

 formed. Usually the hyphae are divided into segments 



