This is always easier to see if you look directly down on a plant from above. Spiral phyllotaxy means that the leaves (or pairs of leaves) are stepped around a stem, much like the steps of a spiral staircase. However, I’m no mathematician, so the above link below will be better at explaining this than I could ever hope to be. This relates to the Fibonacci sequence and the golden ratio. It can be seen in many aspects of nature (and not just in the plant kingdom). The most interesting arrangement, perhaps, is the spiral. Bedstraws, like this ladies’ bedstraw show this pattern of phyllotaxy. Leaves can also be arranged in a whorl, when more than two leaves appear at one node. Mint plants and maples show this pattern, like many of the plants in this plate I did for HarperCollins flower guide. Leaves can be arranged opposite one another at a node, in pairs. The reason for the variation in leaf layout is both environmental and innate in the plant so generally the purpose is to maximise the amount of sunlight hitting the leaf surfaces of a plant (and thus maximising space available for photosynthesis). This is a wild and wonderful subject, and maths figures heavily. There’s a term to describe the way the leaves of a plant are attached to the stem: phyllotaxy, which directly translates from the latin as “leaf order”. Phyllotaxy: How a leaf is attached to the stem Here, parallel venation is illustrated with the autumn crocus. Members of the lily and onion (Allium) family show this, so do grasses. The other layout of veins has them running parallel to each other. Leaves often show pinnate netted venation the more familiar pattern that you might see in a holly, or beech leaf skeleton and you can see it in this honeysuckle study. This can be palmate netted venation, where the veins spread form one central point like fingers from a hand (think of a nasturtium or geranium). The first is netted venation, where the leaf veins form a lace-like skeleton of veins. When you’re drawing a leaf you need to notice this, both in terms of getting the leaf looking correct, and also because it helps when plotting in shadows and lights. Venation patterns are the layout the network of veins form. So this shows many of these margins on one page. For more please follow the link to the University of Rochester’s informative illustrated article.īelow is an illustration done for Rodale’s 21st Century Herbal by Michael Balick. This has covered some basic aspects of leaf margins. This is the case with this Golden opposite leaved saxifrage. Serrate margins are leaf margins where the teeth are like those of a saw, continuous and forward pointing (like the sweet chestnut).ĭentate margins have continuous teeth which point outwards (like the strawberry).Ĭrenate margins are pretty much the same as dentate ones, but the teeth tend to be rounded. This covers three terms serrate, dentate, and crenate. These protrusions either come from the midrib (as with the dandelion and oak) and are described as pinnately lobed or they spread like fingers from a hand (think of a maple or ivy leaf) then the term is palmately lobed.Īnother margin type is toothed. These can be spiky or rounded (so think of a dandelion and an oak leaf). There are lobed margins, where the blade of the leaf is divided into protrusions. There are no teeth or notches taken from the edge, it’s smooth and complete. Entire marginsĪ smooth edge is called an entire margin. What is a margin?Ī margin refers to the edge of the leaf. If you find any mistakes feel free to tell me I’m not a botanist, just a keen and interested amateur. The examples are all illustrations I’ve done over the years. This week I tackle margins, different venation patterns, and key ways that leaves are attached to the stem. The terms discussed are in bold text. In last week’s blog I discussed simple vs compound leaves and basic leaf shape.
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