PROPAGATION OF PLANTS. 13 



mined by the aid of the most powerful microscopes. But 

 down here, at or near the unit of vegetable life, we find 

 perfect plants that consist of only a single cell, and 

 among the most familiar of them is the yeast plant 

 (Torula cerevisice) A cluster of 

 these one-celled plants, highly 

 magnified, is shown in figure 1. 

 There are different species of yeast 

 plants, each of a different form, 

 and all may be propagated, under 

 proper conditions, as readily as 



Fig. I.-YEAS. CELLS. P^tsof higher orders. TheBac- 

 tena are among the most mrnute 

 and obscure race of one-celled organisms, and the in- 

 terest in these is increased on account of their frequent 

 association with many of the diseases of the higher 

 order of plants and of ani- 

 mals. There are hundreds 

 and thousands of species of 

 these minute one-celled plants, 

 and they assume a great va- 

 riety of forms; some are sim- 

 ple round dots floating in 

 liquid, others in chains of 

 cells, while some species are 

 ornamented in the most intri- 

 cate geometric patterns, while 

 others are oval, long, or spread 

 out in a fan-shape, as shown 

 in the one-celled alga (Lic- 



, 7 ,., , Fig. 2. ONE-CELLED ALGA. 



mophora splendida), figure 2. 



While these minute one-celled plants play an impor- 

 tant part in the development and continuation of plant- 

 life, still their small size has, in a measure, prevented a 

 very general acquaintance with their structure and 

 properties, as well as making it somewhat difficult to 



