SUMMER MEETING. 



41 



G. L. Teller : The starch grains 

 found in the tuhers of the common 

 potato, when fully formed, are flat- 

 tened, irregular bodies, about one and 

 one-third times as long as broad, per- 

 haps .003 of an inch long, and usually 

 broader at one end than the other. 

 They are made up of alternate strata 

 of different densities, i. e., having differ- 

 ent amounts of water. The strata are 

 eccentric to a tiny globular portion 

 known as the nucleus and give the 

 the appearance of being marked 



gram 



STARCH 

 SOLANUM 



JAMES1J, Tom. 



^oXoXo. 



Fig. 11. 



Fig. 10. 



with alternately dark and white irreg- 

 ular lines eccentric to a point near the 

 narrower end. 



The granules found in the tubers of 

 a wild potato from Arizona (Solan u/n 

 Jamesii) are smaller than those 

 above described, proportionally much 

 narrower, more regular in outline and 

 thickness of strata, and nearly always 

 have the nucleus near the broader 

 end. 



[For illustrations you will consult 

 figures 10 and 11.] 



heard something of the structure of a 



hairs on the surface, 



nettle; the palisade 



The account of 



Dr. Beal: We have now seen and 

 leaf ; its epidermis, stomata, the young hairs and the old 

 the poisonous and moving protoplasm in the sting of a 

 cells, the chlorophyll granules, the starch formed in the leaf 

 the structure of the leaf will conclude with some illustrations and explanations 

 of the frame-work of, or skeleton of the leaf. I introduce to you 



H. R. Case: I have here in my hands some very large leaves of the rhu- 

 barb, or pie plant. Here maybe seen prominent branches known as the frame- 

 work of the leaves. Small branches are very numerous, making a fine net- 

 work. In each vein or rib is one or more fibro-vascular bundles. 



The frame-work of leaves and stems is made up of different kinds of tis- 

 sues, among the most important of which are the sieve and tracheary tissues. 



In the sieve tissues the end walls of the cells are perforated, in order that 

 the protoplasm and watery substances may pass from one end of the plant to 

 another with perfect ease. 



In the tracheary tissues, or, as more commonly called, vessels, the end walls 

 have entirely disappeared, leaving long tubes with tips often coming to a point. 

 These vessels vary much in shape and in their markings. Probably the most 

 common form is the spiral vessel, iu which the cell walls have thickened in a 

 spiral manner, giving the appearance of a narrow band of cellulose material 

 around the outside of the ceil. These spirals usually turn from right to left, 

 or in the direction of the hands of a watch, but are found turning in the 

 opposite direction, as in the young twigs of the Scotch pine. These vessels 

 terminate by turning to one side and coming to a point, as seen in the thick 

 limbs to some cacti. 



We often have interrupted or double spirals, in which the bands pass in both 

 directions in the same vessel. 



