This exercise made me aware it is sometimes easier to draw the negative shapes between the leafs and branches of plants rather than draw round the flower or leaf. The marker started running out toward the top. I quite like the effect. It seems to indicate the light source also I like that you can see the the way the marker has been applied.
This silhouette effect could be effective as a back drop for future paintings/drawings concentrating on tone and form. Mix the two styles up.
Still need to work on those man made ellipse shapes.