SECT. I 



MORPHOLOGY 



11 



o^■ganised plants, it is termed a thallus. When the thaUus is 

 differentiated into members analogous to those of the higher plants 



some confusion may arise 



from the same names 



being used for parts x^ 



which, since their origin 



has been distinct, are ^'«- 2--s««'^«''<'™2/^f« 



, - ' cerevisiae. 1, Cells 



not homologous. 



^jjwiiu. without buds; 2 and 



The simplest form 3, budding cells, (x 

 that we can imagine for ^'**^'^ 

 an organism is that of a sphere, and this 

 is actually the form of some of the lower 



Connnencenient of divisioii ; B, plants. A grCCU grOWth oftCn SCCn On 

 (to the left) shortly after division; ^ ^^^jj^ consists of an aggregation of 



C, a resting stage, (x 540.) ^ . . P* . *, , ■,■ 



the microscopically small spherical bodies 

 of Gloeocapsa polydermatica (Fig. 1), an Alga belonging to one of the 

 lowest divisions of the vegetable kingdom. The single plants of the 

 Beer-yeast (Saccharomyces cerevisiae) are ellipsoidal ; but, from their 



Fk;. 1. — Gloeocapsa polydermatim. A, 



/V-3 



o 



Fig. 3. — Pinnularia viridis. A, Surface 

 view ; B, lateral view, (x 5-tO.) 



Fio. 4. — Bacteria from deposits on teeth, a, 

 Leptothrix hiiccalis; a*, the same after treat- 

 ment with iodine ; 6, Micrococcus ; r, Spiro- 

 cliaete dentium after treatment with iodine ; 

 d, Spirillum sprUigenum. (x 800.) 



peculiar manner of growth, by budding, they form lateral outgrowths, 

 and thus often appear constricted (Fig. 2). Cylindrical and also disc- 

 shaped forms are shown by various Algae. The Diatomeae (Fig. 3), 



