为了从解剖学角度探究中国特有珍稀濒危植物小溪洞杜鹃（Rhododendron xiaoxidongense W. K. Hu）的环境适应性机制和濒危机制，采用扫描电镜对其花粉特征及种子表面纹饰进行观察，并运用常规石蜡切片法对其叶片、幼茎、侧根和幼果的解剖结构进行研究。结果表明：小溪洞杜鹃的花粉为复合型四合体，单粒花粉近球形，表面具黏丝，并具3个萌发沟。种子表面具肋纹且有明显的背腹面之分，两端具明显的翅。幼果的心皮边缘内卷，将子房分为8个心室，胚珠沿中轴胎座排列于两侧。叶为典型的异面叶，上表皮为复表皮，由2层排列紧密的不规则扁长方形表皮细胞组成，栅海比为0.49，而下表皮则由1层椭圆形表皮细胞组成，并分布有气孔；主脉仅有1个维管束，近圆形，并向叶片上表皮延伸形成维管束鞘延伸区，木质部位于维管束鞘中心位置且较为发达，韧皮部位于木质部四周，属于周韧维管束型。茎由表皮、皮层、次生韧皮部、次生木质部和髓组成，薄壁组织细胞内含有晶簇，无周皮，处于初生结构向次生结构的过渡阶段。侧根维管柱位于栓内层内，次生韧皮部面积较小，次生木质部较发达，木射线细胞在次生木质部呈放射状环绕排列。综上所述，小溪洞杜鹃为杜鹃花属（Rhododendron Linn.）植物的原始类群，营养器官和生殖器官的解剖结构特征既是该种的分类参考依据，也是其适应生境的一种表现。

In order to explore the environmental adaptation mechanism and endangered mechanism of Rhododendron xiaoxidongense W. K. Hu, a rare and endangered plant endemic to China, from an anatomical perspective, the pollen characteristics and seed surface ornamentations were observed by using a scanning electron microscope, and the anatomical structures of its leaves, young stems, lateral roots, and young fruits were studied by using routine paraffin section method. The results show that the pollen of R. xiaoxidongense is a compound tetrad, and the single pollen is nearly spherical, with sticky silk and three germination furrows on the surface. The seed surface has a ribbed pattern and a distinct dorsal-ventral division, and both ends of the seeds have obvious wings. In young fruits, the edges of the carpels curl inwards, dividing the ovary into eight ventricles, and the ovules are arranged on both sides along the central axis placenta. The leaf is a typical dorsiventral leaf, the upper epidermis is a multiple epidermis, composed of two layers of tightly-arranged irregular oblong flat epidermal cells, the ratio of palisade tissue to spongy tissue is 0.49, while the lower epidermis is composed of one layer of oval epidermal cells and is distributed with stomata; there is only one vascular bundle in the main vein, which is nearly circular and extend towards the upper epidermis of the leaves to form. a bundle sheath extension area, the xylem is located at the center of the vascular bundle sheath and is relatively developed, and the phloem is located around the xylem, belonging to the peri-tough vascular bundle type. The stem consists of the epidermis, cortex, secondary phloem, secondary xylem, and pith, the parenchyma cells contain crystal clusters, there is no periderm, and the stem is in the transitional stage from the primary structure to the secondary structure. The vascular cylinder of the lateral root is located within the phelloderm, the area of the secondary phloem is relatively small, while the secondary xylem is relatively developed, and the xylem ray cells are arranged radially around the secondary xylem. In conclusion, R. xiaoxidongense is a primitive group of Rhododendron Linn. species, and the anatomical structural characteristics of vegetative and reproductive organs are both a reference for the classification of this species and a manifestation of its adaptation to the habitat.