<3 The Heart <3


Have you ever wondered why the heart symbol is equated with love? After all, it bears no physical resemblance to an actual human heart. There have been many explanations put forth regarding this association, mostly dealing with parts of the female anatomy, but one hypothesis is quite intriguing and, if anything else, makes for a pretty great tale.

It all starts with the Romans. They were known for a plethora of accomplishments and advancements in technology as well as some serious tribalism, but one thing is for certain, they were an amorous lot! The Romans enjoyed love making and indeed were some of the first people to use certain forms of contraceptives. There was one method of birth control that the Romans really seemed to prefer - silphium.

We aren’t really sure what exactly silphium was but what we do know is that it is most likely a close relative of fennel. This puts it in the carrot family. The reason we don’t know what it was for certain is because it is believed to be extinct. The Romans quite literally fornicated it out of existence. Because it is no longer extant, we cannot speak to the efficacy of its contraceptive properties but the Romans sure believed in it. It became so popular that it was worth its weight in silver. The thing that made it so coveted was that it didn’t seem to be able to grow anywhere but a narrow swath of land along the Mediterranean Sea. It was so rare and so highly sought after that poaching was a regular theme. On top of that, cattle that grazed on it were said to have delectably flavored meat. These factors coupled with desertification of its habitat were too much for a plant with such a narrow range. It was pushed over the edge into the bottomless pit of extinction. 

So, what does this plant have to do with the heart symbol? By examining Roman illustrations of the plant it was discovered that the seeds were heart shaped. They believe the Romans began to associate the shape of the seed with the ability to have lots of sex without the risk of child birth. It became such a powerful symbol that they even went as far as to stamp it on their currency (pictured here). Whether or not all of these facts represent the true story is up for a lot of debate. I am, after all, no historian. What can’t be denied is the popularity of silphium during this period in Roman history. Think about that the next time a relative sends you a heart shaped Valentines Day card!

Ferula tingitana  is believed to be the closest extant relative of silphium.

Ferula tingitana is believed to be the closest extant relative of silphium.

Photo Credit: Expedition magazine Vol. 34, Nos. 1-2, 1992 om p. 62 and Ruben0568 (Wikimedia Commons)

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The Crazy World of Cycad Sex

When we think about plants, swimming ability generally doesn't come to mind. As kids we learn that one of the major differences between plants and animals is that plants generally can't move on their own volition. Certainly there are exceptions to this rule - sensitive plants and Venus flytraps to name a few. However, there are plants out there in which swimming is a crucial component of their life cycle. Though it isn't the plant itself that does the swimming, some of the ancestral plant lineages alive today have motile sperm!

Swimming sperm is a throwback to the early days of plant evolution. Because they arose from aquatic algae, a sperm's ability to swim to an ovule helped increase the chances of reproduction. Today we see this adaptation in plants like liverworts, mosses, and ferns, which still require water to complete their life cycle. However, swimming sperm are not restricted to the cryptograms. This adaptation also can be found in cycads (as well as ginkgoes). Their sperm are super strange too. They look like little seeds covered in concentric rings of beating flagella. Unlike cryptograms, however, their swimming ability doesn't come into play until pollen comes into contact with the ovule.

Cycads are either male or female. Each produces cone-like structures called strobili. This is where the magic happens. When pollen from a male plant finds its way onto the ovule of a female, it does something quite strange. It fuses with the ovule and begins to grow. In essence it acts almost like a parasite, sucking up nutrients from the ovule tissue and destroying it in the process. This is okay because once this happens, these tissues soon become obsolete. What matters is the female gametophyte, which is embedded inside the ovule.

The pollen begins to grow a tube down into the ovule. Once it has gained enough energy, the pollen will then burst and release its sperm. This is where the flagella come in. Each sperm is like a tiny submarine, capable of swimming around inside the ovule until it locates the female gametophyte. Then and only then is fertilization accomplished. Pretty wild for an otherwise sessile organism, wouldn't you say?

Photo Credit: http://www.slideshare.net/ericavanet…/lab-5-origin-of-plants

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