(30 



both the work of foliage leaves and that of bearing the spore- 

 cases (ferns) , while in other cases some of the leaves have be- 

 come changed into mere spore-bearing organs (horse-tails). 



The flowering plants (cases 56 to 128) comprise a single 

 subkingdom, the Spermatophyta, or seed-bearing plants. 

 This extensive group seems to have followed two indepen- 

 dent lines of development and consequently the plants fall into 

 two well marked groups, the first being the gymnosperms, 

 cone-bearing plants, or plants in which the seeds are borne 

 exposed in variously shaped cones (cases 56 to 58). This is 

 a comparatively small group, but exhibits great diversity, in- 

 cluding plants ranging from straggling shrubs or vines to the 

 largest trees. The leaves, too, vary from structures resem- 

 bling needles or scales to expanded fern-like structures of 

 considerable variety 7 . In a former geological age these 

 plants were the dominant seed-bearing plants, but now the 

 second group of the spermatophytes largely predominates; 

 namely, the angiosperms, fruit-bearing plants, or plants in 

 which the seed is borne in a seed-case. These plants also 

 existed in the later geological ages, and now form the most 

 important and conspicuous part of the vegetation of the earth. 

 The fruit-bearing plants (cases 59 to 128) fall into two divi- 

 sions, the one in which the seed contains a single leaf, the 

 monocotyledons (cases 59 to 71) ; the other in which the seed 

 contains two leaves, the dicotyledons (cases 72 to 128). 



b. Microscope Exhibit. The exhibition microscopes occupy 

 small stands in the west wing of the second floor. In front 

 of the windows on the right as one enters the wing are shown 

 a few of the simplest and smallest forms of plant life. Under 

 the first microscope is a preparation showing the vegetative 

 condition of one of the slime-moulds, organisms in which 

 the characteristics of plant and animal are so little differen- 

 tiated that it is nearly impossible to affirm with confidence 

 that they belong either to the one kingdom or to the other. 

 In the vegetative stage — the stage here exhibited — the 

 organism is strikingly similar in its essential attributes to 

 some of the lower animals. Later, in the reproductive stage, 



