230 Introduction to Botany. 



are dioecious. Do both kinds appear at the same time ? 

 Can the pollen be blown about readily by the wind, or is it 

 sticky, so as to require the aid of insects in pollination ? 



What is the nature of the stigma ? Do both staminate 

 and pistillate flowers secrete nectar ? Prove the following 

 statement from Sprengel : " Whoever examines the pistil- 

 late flowers of willows will find a drop of nectar on their 

 nectaries." Draw a staminate and a pistillate inflorescence 

 showing the form of the bracts subtending the flowers. 

 Draw a staminate and a pistillate flower from the best 

 point of view to show all of the parts. Make a drawing 

 of a mature fruit, showing how the capsule breaks open 

 and how the seeds are disseminated. 



Populus monilif era (or other species) . — Cottonwood. 



Draw a branch showing the difference between flower 

 buds and leaf buds as to position, form, and size. Note 

 how the buds are protected. Draw a leaf in position on 

 the branch, showing its light relation, — that is, its position 

 relative to the strongest incident Hght. Where do these 

 trees most abound .'' Draw staminate and pistillate inflo- 

 rescences, showing their position with reference to the verti- 

 cal. Show the forms of the scales subtending the flowers. 

 Draw staminate and pistillate flowers from the best point 

 of view to show the number, form, and position of the 

 parts. Is the pollen sticky, or is it dry and easily carried 

 about by the wind .? Draw the stigmas on a large scale, 

 and decide whether they are well adapted to catch and 

 hold pollen wafted to them by the wind. Note whether 

 insects visit both pistillate and staminate flowers. When 

 the capsules are ripe, notice how they break open, how the 

 hairs on the seeds spread apart, and how the seeds are 

 scattered. 



