40 



STATE HORTICULTURAL SOCIETY. 



torn of the cell is the nucleus, a thickened mass of protoplasm. The move- 

 ments in the main streams are most always in opposite directions. After a 

 lapse of some fifteen minutes the movement stops, beginning again after a 

 short time, but in a contrary direction. The smaller strings change their posi- 

 tions, sometimes uniting with each other and with the main currents. 



The hair from the nettle consists of but one cell. The end of the hair is 

 very brittle and breaks easily when touched. It is the protoplasm escaping 

 into the pricked part of the hand which causes the peculiar stinging sensation 

 felt by a person. The streaming movement of the protoplasm extends 

 throughout the whole length of the cell but can be best observed near the mid- 

 dle of the hair, because here the movement is very much faster than at the end. 

 Only a small section of the cell can be seen under the miscroscope at one time. 

 Here there were from two to five main currents or streams and also many 

 more smaller strings than in the above specimen. Here, as in the hairs of 

 tradescantia, the movements in the main currents were in opposite directions, 

 but there appeared a greater change in the positions and movements of the 

 smaller strings. Two streams would often unite to form one and one stream 

 would often separate into two or more. New strings would break forth from 

 the large. streams. The change in the positions of the strings was very rapid, 

 oftentimes passing out of the focus of the miscroscope. This everchanging 

 movement of the strings of protoplasm made it very difficult to represent them 

 satisfactorily. The changing movements could be studied for hours with ever 

 increasing interest. 



Dr. Beal : We shall learn still more in regard to the structure of a leaf by 

 hearing something about the palisade cells from R. H. Cary : 



Beneath the upper epidermis which 

 is destitute of chlorophyll, in the leaf 

 of the pumpkin there are some cylin- 

 drical cells placed with one end toward 

 the epidermis. These are called pali- 

 sade cells. In the leaf of the pumpkin 

 there is usually one row of palisade cells ; 

 in the cotyledon there are two rows 

 placed end to end , while in the leaf of 

 the compass plant there are three rows on 

 each side of the leaf. The palisade cells, 

 like most other cells of parenchyma in 

 the loaf, contain granules of chlorophyll. 

 Figure 8 shows vertical sections and cross sections of palisade cells with dots 

 representing the granules of chlorophyll. 



Figure 9 shows two sorts of cells of a 

 leaf of Selaginella,m which the granules 

 of chlorophyll are few in number but are 

 unusually large. 



Dr. Beal : Starch is formed in the 

 granules of chlorophyll, usually in the 

 leaves, and is often carried to roots, root- 

 stocks, seeds, tubers, etc., where it is 

 deposited as a store of nourishment for 

 the future use of the plant. One mem- 

 ber of our class has been comparing the 

 starch of our common potato with that 

 of a wild potato from Arizona. We 



6fl#W»rt 5la« 



Fig. 8. 



Chlorophyll 



OF THE 



Selacinella. 



ABOOODWlrc 



fcpTSHar? *uw 



Fl(i. 9. 



shall next hear from G. L. Teller 



