12:20 AM, Sunday July 19th 2020
Starting with the arrows, you are drawing them such that they flow smoothly through space, although you're not allowing the distances between the zigzagging sections to compress more and more as they move away from us. Remember that perspective applies both to the size of objects, and to the distances between those objects - meaning that the further back we get, the more that spacing needs to tighten up.
Moving onto your leaves, one interesting thing I'm noticing is that you appear to apply a lot of confidence and flow to your lines when doing the second step - that is, drawing the simple outside edges of the leaves - but not so much to the first step (defining how the leaf itself flows through space). As a result, they tend to come out feeling as though they're somewhat flat. This suggests to me that when tackling this first step, you're likely thinking ahead to the next, before ever having laid down that first mark. It's critical that when you draw these leaves, you think about how that single, first line, defines its movement through space. One thing that can help to achieve this is to add a little arrow head at its tip, to remind yourself of the fact that the line itself represents motion - not just a static pillar upon which to build.
There are a couple other things that stand out to me with this exercise:
You are approaching a lot of constructional principles correctly - you lay things down as scaffolding, and you build atop them directly, not treating them as loose suggestions but rather making sure those relationships between one phase and the one preceding it are tightly bound. It really is the flow lines that are holding you back, because it's that first line that doesn't establish how the leaf moves through space, and so the rest of the leaf fails to do so as well.
In a number of cases you appear to be confusing the basic artificial contour lines we draw along the surface of the leaf with representations of the textural veins you'll see in your reference. These are different things - contour lines are just lines, artificial, made-up things to help us understand how that surface exists in space. The veins, should we try to capture them, are texture, and therefore would be drawn using textural techniques covered in lesson 2 - specifically capturing the shadows they cast on their surroundings in order to imply their presence.
Don't try to apply form shading to your leaves, for the reasons explained here form shading is not to be included in the drawings for this course unless otherwise explicitly stated. When adding texture to a drawing, it's easy to think that it just means making it pretty - that is not the case. Where construction helps the viewer understand what it'd be like to manipulate the given object in their hands, texture conveys what it'd feel like to run their fingers across its surfaces. It is not about rendering, not about making things look nice or impressive. Shading for shading's own sake is just a decoration, and will distract you from the main points of the course.
Moving onto your branches, just a few small notes. Overall you're doing decently, although aren't always abiding by the instructions:
You aren't consistently extending your segments fully halfway to the next ellipse. As shown here, extending it halfway to the next ellipse provides a good bit of overlap between it and the next segment, allowing them to flow more smoothly together. Making a point of having them overlap like this, with the next segment using the last one as a runway, will help to avoid those visible 'tails' you get where the lines diverge.
I'd definitely recommend drawing these bigger - drawing smaller will both limit your brain's ability to think through spatial problems, and will also discourage you from engaging your whole arm when drawing.
While there are a few issues I want to address in your plant constructions, you're largely doing a pretty good job. Again, you're following most of the main principles of construction (though when drawing some petals with slight waviness to them you do sometimes jump ahead a step instead of building those petals as simply as possible first), and you're doing a good job of drawing through each and every form in its entirety, which definitely helps you grasp how they relate to one another in 3D space.
One thing that jumps out at me rather quickly is the tendency to use lines when capturing certain textural qualities, like the little ridges and valleys in your petals. All texture should be captured using cast shadow shapes, not lines, and you can force yourself to do this by drawing those textural marks like this. Forcing yourself to use this two-step process will make it impossible for you to fall into the habit of drawing them with simple lines.
Again, don't confuse form shading for cast shadows - form shading should be left out of your drawings entirely. Furthermore, filled areas of solid black should be reserved for cast shadow shapes only. Don't attempt to fill in an area to capture its local colour, just because it appears darker in your reference image. An example of this mistake is how you approached the tips of the bottom right flower on this page. Solid black areas should always mean cast shadow. As for local colour (that is, the actual colour of a given surface when all lighting information is ignored), we don't concern ourselves with it at all and instead treat every object like it is of the same flat colour.
As you got into the last page, I started noticing a tendency to add really thick line weight in specific areas of your flower petals. I'm unsure of what you're trying to achieve with that, but it definitely makes it more difficult to piece together how those forms are meant to relate to one another. In general, remember that line weight should be used in very specific areas to clarify how one form overlaps another. Don't apply it to the entire length of a line, or any sort of an extended area. Always apply it to a specific point, to clarify a specific overlap, and then blend that weight back into the original line.
Furthermore, line weight should be subtle - it is only a matter of making a line relatively thicker than another, something that the viewer's subconscious will pick up on, but not more than that. If you want to make things much heavier, then you're getting into the territory of cast shadows, which behave distinctly differently from line weight (in that they're cast upon another surface and don't cling to the silhouette of a given form). Also, when adding line weight be sure not to trace your lines - use the ghosting method as you would when drawing the initial linework, as this will help you avoid focusing too much on how a given line exists on the flat page, which is a common problem when tracing back over things.
All in all you do have a number of areas to work at, but I think you've established a good base of how you approach construction as a whole. I'll go ahead and mark this lesson as complete.
Move onto lesson 4.