As for engravings, Durer's work was restricted to portraits and illustrations for his treatise. The portraits include Cardinal-Elector Albert of Mainz; Frederick the Wise, elector of Saxony; the humanist scholar Willibald Pirckheimer; Philipp Melanchthon, and Erasmus of Rotterdam. For those of the Cardinal, Melanchthon, and Durer's final major work, a drawn portrait of the Nuremberg patrician Ulrich Starck, Durer depicted the sitters in profile, perhaps reflecting a more mathematical approach. Despite complaining of his lack of a formal classical education, Durer was greatly interested in intellectual matters and learned much from his boyhood friend Willibald Pirckheimer, whom he no doubt consulted on the content of many of his images. He also derived great satisfaction from his friendships and correspondence with Erasmus and other scholars. Durer succeeded in producing two books during his lifetime. "The Four Books on Measurement" were published at Nuremberg in 1525 and was the first book for adults on mathematics in German, as well as being cited later by Galileo and Kepler. The other, a work on city fortifications, was published in 1527. "The Four Books on Human Proportion" were published posthumously, shortly after his death in 1528. 

What might one be surprised about Durer's approach to his drawings?


She led the way into the cheerful schoolroom, where big girls and little girls were sitting about, amusing themselves in the quiet of a long Sunday afternoon.  Several of the younger children ran to her as she came in, and stood holding fast to the folds of her black habit, staring up at the strangers, while she explained the kind of instruction given, the system, and the order reigning in each department.  Finally, she persuaded a little girl, only six years old, to take her dusky face out of the long flowing veil of the nun, and show how quickly she could read a sentence that Sister Winifred wrote on the blackboard.  Then others were called on, and gave examples of their accomplishments in easy arithmetic and spelling.  The children must have been very much bored with themselves that stormy Sunday, for they entered into the examination with a quite unnatural zest.  Two of the elder girls recited, and some specimens of penmanship and composition were shown.  The delicate complexion of the little nun flushed to a pretty wild-rose pink as these pupils of hers won the Colonel's old fashioned compliments. 

What day did the nun enter the schoolroom with the strangers?


Relying on an animal to come by is risky. A flower may have to wait a long time for the right animals to come by. What if one never passes close enough to the flower? Hoping the wind will blow is also risky for a plant. What if the wind does not blow? What if the blowing pollen does not land on another flower? The wind could even blow the pollen over the ocean where it is wasted. Giving free nectar is costly. It is not a good use of the plants energy. A plant uses a lot of energy to produce nectar. Some animals may just drink the nectar. They may not carry off any pollen in return. To improve their chances, plants evolved special traits. For example, they developed ways to hide their nectar. Only certain animals were able to get at the plants hidden nectar. These specific animals might be more likely to visit only flowers of the same species. This was also a benefit for some animals. Animals also evolved special traits to get to the nectar. 


What is risky for a plant with its nectar?