(34) 



sacs, each enclosing eight spores, are ejected with consider- 

 able force. Under two microscopes are shown sections of 

 lichens, illustrating their mode of reproduction and the fact 

 that a lichen consists essentially of two organisms, a fungus 

 and an alga, intimately associated and -constituting what for 

 many purposes may be looked upon as a single organism. 



Then follow specimens of the liverworts or scale-mosses, 

 plants in which the differentiation of the vegetative body 

 into stem and leaves becomes first clearly evident. One of 

 these, a Frullania, has a part of each leaf peculiarly modi- 

 fied so as to form a reservoir for water. By aid of this 

 device, the frullanias and their allies are able to thrive in 

 drier situations than are in favor with most of the order to 

 which they belong. Preparations are exhibited showing also 

 the vegetative structure and methods of reproduction of the 

 true mosses. Especially interesting is the "peristome" of 

 one of the mosses, which is a fringe of peculiar appendages 

 surrounding the mouth of the little urn in which the minute 

 dust-like spores are borne. These appendages move about 

 as a result of changing conditions of moisture and these 

 mechanical movements assist in scattering the spores. A 

 somewhat analogous device is found in connection with the 

 spores of the equisetums or horse-tails, though the appendages 

 in this case are attached to the spores. Following the slide 

 illustrating this feature of the horse-tails is one showing the 

 spores and spore-cases of the common polypody. The spore- 

 case here is provided with a sort of spring, by the action of 

 which the spores are violently ejected, catapult-fashion. The 

 remaining preparations show the structure of the leaf-stalk 

 and root of common types of ferns. 



c. Local Flora. In this collection it is designed to illus- 

 trate every plant-species growing naturally or without culti- 

 vation within one hundred miles of New York Citv. For 

 the most part specimens of the plants themselves are used, 

 but in cases where the structure of the plants renders this 

 method undesirable, or impossible, a photograph or a draw- 

 ing is substituted for the plant-specimen. This collection 



