Sažetak In this work is examined the anatomical structure of the species Drypis spinosa L., one of the most important representatives of the vegetation of the rolling-stones in Croatia. The genus Drypis (fam. Caryophyllaceae subfam. Silenoideae) is represented by two subspecies, according to the earlier investigations (particularly those of Wettstein and M u r b e c k): Drypis spinosa subsp. Linneana and Drypis spinosa subsp. Jac- quiniana. The first subspecies covers the rolling-stones of the mountains stretching from Carniola to Greece, and in the central part of the Apennines, where it builds a special, phytoce- nological, excellently characterized community Drypetum Lin- neanae Horv. The second subspecies is represented in the Kvar- ner-Istrian area, where it is found on the rolling-stones near the sea, in a very well examined community —- Drypetum Jacquinianae H-ic.
As the two subspecies are morphologically different, and also from the point of view of botanical geography and phyto- cenology, so it is the aim of this investigation to find out if there are differences in the anatomical structure. As in the existing literature about the anatomical structure of the genus Drypis there are almost no details, it has also been interesting to examine the anatomical structure of this genus comparing it with other representatives of the family Caryophyllaceae. It seemed to us important to examine the anatomical structure of both subspecies, so that the possible anatomical differences could have a considerable influence in deciding the systematic relations of both relationships.
The anatomical examinations of the vegetative organs of the species Drypis spinosa L. show the following: The root is unusually well developed, better on lime basis then on ground poor with lime. In the primary stage, the root is covered with epiblema and underneath of it is found the primary bark, which ends with endodermis. The central cylinder is found underneath the endodermis which is difficultly distinguishable from the primary bark. It begins with pericam- bium in which peridermis is very early developed and in the middle is found the diarch vessel. The secondary stage begins with the forming of the cork peridermis (after this the external parts of the root fall off), and with the appearing of the secondary xylem. The xylem, the conducting elements of which are very wide and unusually short netlike tracheae, fuse quickly in a close circle.
It is important, however, that tracheae are regularly arranged in the secondary stage, so that there cannot be distinguished the primary xylem from the secondary one.
In the anatomical structure of the root, both the subspecies do not show any differences.
The stem as the over-ground organ is more exposed to the ecological factors, and shows in the anatomical structure considerable differences between both subspecies. In the primary stage the stem is covered with an epidermis consisting of one layer. The membranes of its cells are tender and of the same thickness. Underneath the epidermis is the primary bark; it contains in the outer part a lot of chlorophyll, which is spread continuously underneath the whole epidermis. The endodermis is the last layer of the primary bark, and it is difficult to distinguish it from the primary bark. The central cylinder begins with the pericycle, where is very early formed the cork peridermis. Six collaterally opened vessels, arranged in a circle are usually found in the inside of the peridermis. It is important for the tracheae that a lot of them are very little lignified. In the middle is the pith, built of parenchym cells.
In the secondary stage there are considerable differences between the part near the ground and the flower-part. The part of the stem near the ground is covered with a very strong epidermis. Underneath it is the primary bark which contains chlorophyll only on corners of the stem. It is very difficult to distinguish the endodermis, which is found round the central cylinder from the other cells of the primary bark (the same as at the flower-part of the stem). The peridermis, which the central cylinder begins with, is developed in the pericycle. It is built of some layers of plate-like cork cells; when the outer parts of the stem fall off, its transverse section is very similar to that one of the root, but it can still be easily distinguished because it contains the pith. In the center is found the vascular system. It consists of collaterally open bundles arranged in a closed circle. In the middle of the stem is the pith which is built of paren- chym cells.
The flower-part of the stem is also covered with epidermis, which is built more delicately than the part near the ground, but still the outer part of the walls is considerably thickened. Underneath the epidermis are found some cell-layers with very thickened membranes which have a mechanical function. They are usually placed in the corners of the stem. The primary bark contains chlorophyll in the peripheric parts, and it ends inwards with endodermis. The central cylinder consists from outside of a ring of sclerenchymatous cells inside of which are some collaterally open bundles, and at last the pith.
It was mentioned before that in the flower-part of the stem the cork had been changed into sclerenchymatous cells. This ring consists of more layers (usually 1—4) of lignified cells. According to the details which Petersen (1888) states, the genus Drypis has not such a mechanical ring, which is found in all representatives of the subfamily Silenoideae. However, it can be seen from the results of this research, that also the genus Drypis has such a ring — and according to this, it does not represent any exception in the mentioned subfamily.
In the anatomical structure of the stem both subspecies show the following differences:
subsp. Jacquiniana more round
the form of the more forecomered stem
the thickness of stem thinner the stem
the epidermis the cuticle the stomata
walls thinner thinner
ordinarily cca 103
walls thicker thicker
ordinarily cca 83
to 1 mm2 simple
to 1 mm2 simple and
mechanical elements scleren- more layers chyma ring
The leaf as organ is most exposed to different ecological influences, and it shows most differences in anatomical structure between both subspecies. The leaf is built dorsiven- tral. From the outside it is covered with epidermis, which has in its corners two or three layers. The membranes of the epidermal cells are of different thickness. On the upper side of the leaf they are in the middle part thin, and on the lower side they are thicker in the middle part and in the corners, whilst between them there are cells with thin membranes. On the thin parts of the epidermis are the stomata, the structure of which corresponds to the structure of the stomata of the other representatives of the family Caryophyllaceae. They border usually with two cells. In mezophyll we can easily distinguish on the upper side the palisade-layer, and on the lower part the parenchyma of the transpiration. Through the mezophyll pass three vessels, which are surrounded by parenchyma cells. The main vessel, which is always mostly developed, goes through the middle of the leaf, and the other sidevessels are often less developed. The vessel is collaterally open, from the lower side there is always the characteristic mechanical tissue, with ligni- fied membranes. With this we usually find druse-crystals of calcium oxalate, which are by their shape different from the other crystals in the mezophyll.
The differences in the anatomical structure of the leaf in both subspecies of Drypis spinosa are the following:
the shape of the leaf
subsp. Linneana thinner and narrower
the membranes thinner, in the corners has one or two layers with a small number of pits, the part with stomata has thin membranes with-pits
cca 100-130 to 1 mm2 regularly of 4-6 cells
smaller and thinner mechanical tissue
thicker and wider
the membranes are thicker, the epidermis in the corners has regularly three layers and more pits; the part of the epidermis with stomata has thicker walls and is interrupted by pits
cca 65-85 to 1 mm2 regularly od 1-2 cells
bigger and thicker mechanical tissue
According to this, there exist differences i the anatomical structure of both subspecies. Almost all these differences developed under the influence of ecological factors. As these differences are considerable, and also constant, I think therefore that, as proposed by Degen (1936), both relationships till now considered as subspecies, could be considered as separate species.