38 



STATE HORTICULTURAL SOCIETY. 



*ti^ d 



STOMAL. 



TRADCSCANTIA 



a from view, 

 across section. 

 O lonoiludinol sccl 



CYPR/PFDIUM. 



d. cross section. 

 CACTUS. 



e.'lront view. 

 i.k.dewii: 



Fig. 3. 



Stomala are pores, by which the inner 

 part of chlorophyll-bearing tissue com- 

 municates with the air. They are found 

 chiefly upon the under sides of leaves, 

 but exist more or less in all chlorophyll- 

 bearing parts. The singular term stoma 

 is applied to the hole through the epi- 

 dermis and the specially formed cells 

 surrounding it. The surrounding cells 

 are all shallow, as may be seen in cross 

 sections. The hole is usually elliptical 

 and may be opened or closed by the 

 spreading or the contraction of the lu- 

 nar shaped cells on either side. These cells are chlorophyll-bearing and are 

 called guard cells. 



In leaves with very regular epidermal cells, as the Tradescantia zebrina or 

 the Cypripedium insigne, the stomata are arranged regularly in rows running 

 lengthwise of the leaves, while in an epidermis with irregular cells, as that of 

 the cactus, there is no apparent regularity in the arrangement of the stomata. 



The stomata of the Marchantia are 

 upon the upper sides of the leaves and 

 are peculiarly constructed. There is 

 an internal cavity and this is* connected 

 with the exterior by means of a round 

 hole. This hole is surrounded by four 

 rows of cells, one above the other like 

 brick work in a well, except there are 

 only two or three cells in a circle, and 

 they do not break joints. The Mar- 

 chantia grows in damp places and its 

 stomata show the most free and direct 

 communication with the air. Fig. 4. 



Opposed to the above is the Nerium, oleander, which grows in a dry country, 

 and the stomata of which show the most indirect and restricted communica- 

 tion with the air. There is an internal cavity nearly filled with hairs project- 

 ing from its sides. In the walls of this cavity are the stomata, eight to twelve 

 in number. They are very small as compared with those of other plants, and 

 have thick guard cells. 



Dr. Beal : To understand fully the nature of living things it is often of the 

 greatest importance to study them when very young and small, and watch 

 them through various stages of growth. I call next on 



1ST. S. Mayo: Very young cells of 

 plants are filled with a living substance 

 called protoplasm. This is active, very 

 sensitive to heat, cold, or other agent. 

 It is the essential thing, without which 

 plants cannot grow or even live. As 

 the cell grows older water enters in 

 such epiantity that the protoplasm can 

 no longer remain diffused throughout 

 the cavity. Vacuoles appear. These 

 are simply spaces in the cells occupied 

 by water containing a little protoplasm. 

 As the cell enlarges other vacuoles ap- 



STOMATA '' 

 MARCHANTIA, 



a from view, 

 b. cross section 



HEHiUM 'OLEANDER ' 

 c cross section 

 a from fiffl. 



LHUEVTi 



VACU01XSW 



NSMa-ra. 



&;?:-jT7 rca 



Fig. 



