文心蘭屬（Oncidium）是蘭科（Orchidaceae）植物，全世界約有700種原生種，主要分佈於巴西至秘魯之南美洲區域。蘭科植物與一般被子植物於花部的外觀形態與發育過程有很大差異。蘭科的花部發育研究中雖已有許多學者提出許多假說，但其中研究過的物種極少，在蘭科花部發育上還有許多問題待釐清。緊密型花粉塊的蘭科植物與一般被子植物於小孢子發育過程中，主要的不同發生於四分孢子體時期之後。本研究利用光學顯微鏡、掃描式電子顯微鏡及穿透式電子顯鏡觀察黃葉瘤唇蘭（Oncidium flexuosum Sims）與該種之一品種南西（Oncidium Gower Ramsey）之雄不孕品系花部形態發育與小孢子發生，並比較兩者之形態發育差異，進而探討南西雄不孕的原因。
在花部形態發育方面，兩種文心蘭的發育過程皆相似。花序始原分化出花始原與苞片始原，繼而花始原陸續分化出六個花被始原（三個花萼始原、兩個花瓣始原與一個唇瓣始原），接著花始原中央再陸續分化出一個可孕雄蕊始原、兩個退化雄蕊始原與三個心皮始原。雄蕊始原與心皮始原後天癒合形成蕊柱，其中退化雄蕊始原的花絲發育特化出文心蘭蕊柱的附屬物（翅）。
文心蘭藥囊壁的型式與一般被子植物不同，其藥囊壁具一層表皮、兩至三層藥室內壁、兩至三層中間層與兩層分泌型營養層。於成熟花粉時，中間層與營養層瓦解消失，表皮與細胞壁不加厚的藥室內壁存在。文心蘭小孢子發育的過程與一般被子植物有很大的差異。黃葉瘤唇蘭的小孢子發育過程，四分孢子體不形成自由小孢子型式、花粉塊四分孢子體依形態與位置區分為外層花粉塊四分孢子體與內層花粉塊四分孢子體，且花粉外壁是於花粉塊外圍形成。南西的花粉塊發育異於黃葉瘤唇蘭之處有：營養層提早於減數分裂時期瓦解、無花粉外壁，且部分生殖細胞中可發現粒腺體與色素體。推測營養層提早瓦解的現象可能為造成南西雄不孕的主要原因。

There are more than 700 species of Oncidium (Orchidaceae) distributed in the region ranged from Brazil to Peru principally. The floral morphology and ontogeny of orchid are very different from the other angiosperms. Some hypotheses about the floral ontogeny of orchid have been proposed. However, quite a few questions about the issue are still needed to be elucidated. The microspore development of orchids is different from the other angiosperms. The orchids’ androecia produce hard pollinia instead of free pollens. The developmental processes of pollinia and free pollens are identical from the beginning to the tetrad stage. After tetrad stage, difference begins. In this study, we observed the floral and microspore development of Oncidium flexuosum Sims and its male-sterile line Oncidium Gower Ramsey with light microscopy, scanning electron microscopy, and transmitting electron microscopy. Based on the results of the above observation, we compared the two taxa’s floral and microspore develoment and tried to find out what caused O. Gower Ramsey to become male-sterile.
Both the two above Oncidium taxa have similar process of floral development. The primodia of floral and bud were both differentiated from the inflorescence primodium. Then, six perianth primodia, including three calyx primodia, two petal primodia and one lip primodium, were differentiated from floral primodia. At last, the primodia of one fertile stamen, two vestige stamens, and three carpels were differentiated at the center of floral primodium. The stamens and carpels develop together into the column. A part of filament derived from vestige stamens becomes into the wings.
The anther wall structure of Oncidium is very different from the other angiosperms. It includes one layer of epidermis, two or three layers of endothecium, two or three layers of middle layer, two layers of secretory tapetum. The microspore development of Oncidium is different from the other angiosperms, too. For example, O. flexuosum does not produce free spores. Instead, the outer pollinium tetrads and the inner pollinium tetrads were differentiated. The exine was formed outside of the layer of pollinium. The difference of the microspore development between O. flexuosum and O. Gower Ramsey are the earlier degeneration of tapetum at meiosis stage, the absence of exine, and the existence of mitochondria and plastids in some generative cell, etc. We speculate the above difference might be the reason of the male-sterility of O. Gower Ramsey.

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