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Two plants surviving on the pavement edge

Two plants surviving on the pavement edge

Plants living between the pavements and buildings exist in an extreme environment. As well as having to grow where there is hardly any substrate, they may be subject to herbicide applications, rock salt, car exhausts, dog fouling, and trampling. There are massive fluctuations both in temperature and the availability of water. The sketch above is of two species that occupy exactly the same niche. In this post I am looking at the plant on the right hand page of the notebook.

Between the pavement and building

Between the pavement and building

The plant has lobed leaves that appear to be in a basal rosette. As there are no flowers it is an opportunity to test my copy of Poland and Clement(2009). The first pages of the book (even before the title page) has a series of photos on the inside front cover that illustrate the main terms used in the ‘Key to Major Divisions’ on the opposite page. (This page is repeated on p9). The Key to Major Divisions is

‘Based primarily upon the increasing degree of leaf dissection’

which effect means that it starts with the simple leaves and goes on to describe the more complex ones,( horsetails, ferns. clubmosses and conifers are in the key but not dealt with in detail on this page). My leaf is simple in that it is not consisting of separate leaflets. Under the heading simple there are then 3 choices in the key; entire (margin without teeth, lobes etc.); margin toothed, but not lobed and margin lobed (maybe toothed).

As my plant clearly has lobes I then go to the next choice which is leaves opposite or alternate, and I think it is the latter which takes me to Division P. (Page 10 has useful notes on leaf arrangements). Divisions are arranged alphabetically so I am now at p 287. The first question is about latex and I am fairly sure there is none here so having established the plant is spineless the next set of choices is concerned with the presence or absence of stipules (of small appendages at the base of the leaf stalk or petiole). I can’t see any stipules so the decision comes down to hairs.

Cottony or woolly hairs at rosette centre?

Cottony or woolly hairs at rosette centre?

Are these the cottony hairs at the rosette centre, I’m not that confident but I opt for Group PO. Now this is where it gets difficult to keep track of the indentations on the keys because this Group PO is spread over a couple of pages. I can see the leaves have septate (many celled, mine look like tiny strings of pearls) hairs that are without glands (Uses the term viscid without explanation; tacky/sticky?). The choice is then between a perennial rhizomatous plant and an annual (rarely bi-annual) one. Its quite difficult to tell whether something is annual or perennial but it does say there are stomata on both sides of the leaf and as these are clearly visible, I plump for Groundsel Senecio vulgaris. 

So what have I learnt? Well this book certainly requires you to look closely at the plant, you have to be prepared to learn different terms, the key requires careful attention where there are more than 2 choices or where these choices are spread over several pages, the line drawings are very useful, but with a bit of effort it does work.

In the next post I will be trying out Poland and Clement on the plant illustrated on the left page of my notebook.

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