Dendrobium: Dissection and Further Studies

I have been unable to find any other illustration of Dendrobium convolutum. There may well be one somewhere, but I have not yet found any published artwork depicting the species. As a result, there is no existing material against which I can compare my observations. This makes it even more important that the dissections are included and that every aspect of the morphology is recorded as accurately as possible. Achieving this requires considerable research and careful study. In fact, I estimate that as much as 70% of the time invested in a botanical illustration can be devoted to research, observation and preparatory studies, with only 30% spent on the final painting itself. This is time well spent, but there is also a need to remain aware of how much time is left before the flowers begin to fade.

Given that there is no immediate deadline for the Dendrobium convolutum painting, and that the plant continues to flower strongly, I decided to undertake further investigations into the floral structure, including a number of simple dissection studies. The flowers of this species are relatively small, measuring only around 3 cm across, and I felt it would be beneficial to include enlarged studies and dissections alongside the final illustration.

I cannot stress enough the importance of working from live plant material. Direct observation allows the artist to study subtle aspects of form, texture and structure that are often impossible to interpret accurately from photographs alone. However, preserved wet specimens are equally valuable, enabling careful examination of details that might otherwise be overlooked and providing a permanent reference long after the fresh material has deteriorated.

Some of the research materials on my desk, I can take time with this plant due to the long flowering period and spend a few hours when I can find the time working on it. On the desk you can see my hand lens (x10 magnification) and proportional dividers as well as a small hand held magnifying glass

At this point I only have a limited number of flowers available for study, making it essential to manage the material carefully throughout both the research and painting process. One of the great advantages of some orchids, though certainly not all species, is the remarkable longevity of their flowers, allowing extended periods for observation and study.

The flower preserved in a small jar of alcohol

Using Wet Specimens

If you recall from my previous posts, the first flower was preserved in alcohol several weeks ago and has remained in excellent condition for the purpose of dissection. This type of waxy flower preserves particularly well in alcohol and is relatively easy to dissect without damaging the delicate structures. The colour is lost during preservation, but this is of little consequence when the primary objective is to study the morphology of the flower.

For my initial investigation, I decided to undertake an 'exploded' style dissection, separating the floral parts and examining them individually. This approach is one of the most effective ways of understanding how the various structures are arranged and how they relate to one another. Following this preliminary study, I intended to produce a series of clean, measured line drawings in ink as reference. Line illustration remains one of the clearest methods of communicating botanical structure, allowing complex forms to be presented with accuracy and precision.

As the work progresses, I also hope to undertake a half-flower dissection to reveal the internal arrangement of the reproductive structures in this bilateral flower. However, at this stage I am reluctant to remove additional flowers from the plant and provides valuable living reference material.

Using the preserved specimen, I began by carefully removing the three outer sepals and the two petals. This left the labellum and the reproductive structures housed within the column intact, making it easier to study their form and arrangement. The flower will dry out quite quickly, so i work quickly and peplace it back into the jar when taking a break.

The deconstructed flower.. Left: The petals and sepals, upper right is the labellum (side view). Just visible lower right is the pollinia (pollen sacs)

Front view of the labellum, the lower lip and the two lateral lobes above, the two rounded callus are just visible in the middle. The column is still attached at the rear

After removing the labellum I was able to investigate the structure of the columns which was best achieved using a ×10 hand lens, this revealed details that were difficult to see with the naked eye. In this study, the anther cap and pollinia have been removed and the female reproductive structure can be seen below. In a live flower, however, removing the anther cap and pollinia has a dramatic effect, the flower will begin to fade and senesce quite rapidly, as its reproductive function has effectively been fulfilled. Once this has occurred, the plant no longer needs to invest energy in maintaining the bloom to attract pollinators, and resources can instead be directed towards seed development.

I then proceeded to draw each component separately, enlarging the scale where necessary to improve clarity. For this process I used proportional dividers, although the same result can be achieved with ordinary dividers, a ruler and some simple arithmetic, whereby each measurement is multiplied by the desired enlargement factor. This allows the artist to maintain accuracy while increasing the scale sufficiently to reveal smaller structural details that might otherwise be overlooked.

The degree of enlargement should always be appropriate to the subject, allowing important morphological features to be clearly understood whilst remaining faithful to the proportions of the original flower. Enlargements that are too small can fail to communicate critical details, while excessive enlargement can make it difficult to appreciate the relationship between individual parts and the flower as a whole. The aim is to strike a balance between scientific accuracy and visual clarity, ensuring that the illustration serves both as an informative study and a useful reference for the final painting.

On the left are the outer sepals and petals. On the right is the labellum, showing its distinctive callus, visible as two dark, rounded, glossy mounds positioned between the upper veined lateral lobes. The labellum is a highly modified petal that plays an important role in guiding pollinators into the flower. As the pollinator enters, it brushes against the reproductive column and may dislodge the anther cap. The sticky pollinia then become attached to the insect's body, allowing the pollen sacs to be carried to another flower where cross-pollination can occur. This highly specialised mechanism is one of the many fascinating adaptations found within the Orchidaceae. Many orchids attract pollinators through deception rather than reward. In this species, the glossy callus on the labellum may mimic the appearance of nectar, enticing insects to investigate. However, no nectar reward is actually provided. Instead, the flower relies on visual cues to encourage visitation and thereby achieve pollination through deception.

On the left is the side view of the labellum with the column above it (anther cap removed). The upper right shows the column and the lower right are the pollen sacs (pollinia), which were remove. Unfortunately I lost the anther cap so will revisit this later with a second flower

Once I had completed these simple measured line drawings, I returned all of the plant parts to the alcohol for safe storage and future reference. Preserved in this way, they remain available for further study if needed.

The next stage will be to undertake a half-flower dissection. This involves making a clean longitudinal cut through the centre of the bilaterally symmetrical flower, but this will need to be a fresh flower, this will reveal the internal arrangement of the floral structures from a side view. Such dissections are particularly valuable in botanical illustration, as they provide information about spatial relationships and structural details that cannot be observed from the exterior alone.

The next dissection will be a half flower cut, which will be made where the dotted line is on the image above. Bilateral (zygomorphic) flowers have inly one plane of symmetry and so a cut down the centre divides the flower into two equal mirror images halves, which will reveal the inner structure of the flower in full.

Alongside the dissection work, I also completed further painted studies of the open flowers on the flower spike, shown below. These studies provided useful practice for the final painting, helping me to better understand the subtle forms, colours and lighting effects present within the flowers. They also offered an opportunity to experiment with the most effective ways of portraying the flowers before committing to the final composition. As with so much of botanical art, these preparatory studies are an essential part of the process, building both familiarity and confidence before work begins on the finished illustration.

The flowers will probably remain in good condition for another two weeks, but I really need to begin the final painting at this stage. One of the challenges of working from living material is balancing the desire to carry out further research and studies against the limited lifespan of the subject. Although the plant is still flowering well, there is always the risk that the blooms may begin to deteriorate unexpectedly, leaving insufficient reference material to complete the painting accurately.

Fortunately, I now have a substantial collection of supporting studies, including measured drawings, dissections and colour notes and studies, which provide a strong foundation for the final artwork. While further investigations can still be undertaken as required, the priority must now shift towards recording the flowers in paint whilst they remain in peak condition. The longevity of orchid flowers is a tremendous advantage for the botanical artist, but even these remarkably durable blooms are always temporary. At some point, research must give way to painting, and that moment has now arrived.

The next phase will be to bring together all of the information to create an illustration that is both botanically accurate and aesthetically engaging. The preparatory work may account for the majority of the time invested in the project, but it is this careful study that ultimately underpins the success of the finished painting when accompanied by a live specimen to complete the work.