Alright, so first, your arrows are evidently pretty wobbly. If you continue practicing this exercise, I recommend making your arrows simpler to start off. Don't jump right into the difficult ones. I would just draw arrows waving back and forth, getting closer to the viewpoint, to start off, because that gets you acquainted with the negative space getting larger as the arrow gets closer, as well as the foreshortening and all that, without giving you too much to worry about. This is what I did, if you want to have a look. Again, it might seem too simple, but we don't want to pile on too many objectives at once here, of course.

The basic shapes of your leaves look nice, but I have to say there's far too much detail, and it's incredibly visually noisy. Remember how the dissections in Lesson 2 worked? And the texture analysis? Every texture, at its brightest, is just white, while the details start to become more obvious as it gets darker (because the shadows are casting off the details). So remember that NOT every vein in the leaf needs to have a shadow, because in reality, not all of them really do. At least, not to a point where we should consider them.

Your branches look alright. There's a lot of bumpiness, though I get that too since it's something that can only really be solved with a lot of practice. Remember to try tapering your line in, gradually increasing the pressure, as you start it. This should minimize that effect and make it look less chicken scratchy. There's also a lot of unevenness to them, which technically isn't WRONG for a natural, wooden branch, but it would be worth the effort to try and keep them consistent anyway as drawing tubes in general can be quite useful.

Now, the first couple pages of plants. Some of the leaves are kind of wobbly and they don't seem to look 3D. I recommend drawing a circle around your flower first, as this will give you a range for all your petals to go. This one I drew of a hibiscus, for example. It helped me a lot to draw that circle you see around the flower to get a guide for the shape of the flower. Also do remember that every petal exists in 3D, and so they turn and sag, and flip around at times.

The top left plant on the second page has a stem with an inconsistency with the rest of the plant. Both the ellipse where the stem connects, and the ellipse to WHICH it connects, should be the same shape, since they're viewed at the same angle. Unless the base of the plant is supposed to be sagging? In that case it will help you in situations like those to put down a couple contour lines, just to help you out while constructing the drawing.

The bottom middle plant on the second page has some really wobbly leaves, too. Remember when you draw a leaf at first you're basically just drawing the gesture of it. The actual EDGES can come later--you'll build those one at a time. Doing the gesture of the leaf, and then the edge, will produce some more convincingly 3D results.

As for the mushrooms, these look pretty good. I don't see any very obvious mishaps so nice work there.

As for the rest of the plants which you gave detail, I have to say, my GOD that is a TON of detail, man. And that's not a bad thing. Actually, I think it looks pretty good. You did a nice job of making it darker in the more shadowy areas to draw the eye to the lit ones. You seem to have done a better job here at making your constructions more three dimensional, which is good. A well-made construction is like a cake without icing. The icing is the detail, but it should still be good without the icing anyway. But yeah, I wouldn't put THIS much detail into all your Drawabox exercises, because it's gonna take forever if you do. I would reserve this kind of detail into the drawings you create for the sake of artwork.

So there's some gesture and flow issues in some things, but just try to keep in mind all the stuff you've learned about 3D space, and the construction tricks to make things easier (like the circles around the petals) and you'll improve with practice. Feel free to practice the branches, leaves and arrows as warmups in the future. Branches in particular will be useful for drawing insects, with their antennas and all. And remember too, detail is nice, but it's not a vital part of learning construction, so don't worry about it TOO much.