Parasitic flowering plants are characterized by the development of an organ known as haustorium, which has evolved in multiple independent angiosperms clades. The haustorium has also been deemed “the most plastic of organs” due to its ability to accommodate physiological and anatomical differences between the parasite itself and its host plants. This is achieved through the development of vascular connections, which involve the differentiation of various specialized cell types by the parasite. The development, structure, and evolution of the haustorium and the connections it fosters are reviewed here considering all 12 parasitic plant lineages. A multi-level comparison between “model” parasitic plants, such as Orobanchaceae and Cuscuta species, with members of often neglected groups, such as Lennoaceae, Mitrastemonaceae, and Santalales yields the idea of a shared general body plan of the mature haustorium. This proposed haustorium bauplan is composed of an upper part, including structures associated with mechanical attachment to the host body, and a lower part, including all parasitic tissues and cell types within the host body. The analysis of multi-level convergence is also applied here to the comparison between haustoria and other plant organs. Considering the structure, molecular development, and functionality of this organ under the framework of continuum and process plant morphology, I propose the interpretation of haustoria as morphological misfits.

寄生性开花植物的特征是发育成一种称为“抽油草”的器官，该器官已在多个独立的被子植物进化枝中进化。由于它能够适应寄生虫自身及其寄主植物之间的生理和解剖学差异，因此它也被认为是“器官中最具塑性的器官”。这是通过血管连接的发展来实现的，血管连接包括通过寄生虫分化出各种专门的细胞类型。考虑到所有12种寄生植物谱系，在此回顾了吸痰器的发展，结构和演变及其所促进的联系。“模型”寄生植物（如Orobanchaceae和Cuscuta）之间的多层次比较物种，通常具有被忽视的菌群，如Lennoaceae，Mitrastemonaceae和Santalales，从而产生了一个成熟的泌尿生殖器的共同总体计划的想法。提出的这种化脓室由上部和下部组成，上部包括与机械附着到宿主的机械结构，下部包括宿主体内的所有寄生组织和细胞类型。多层次收敛性分析在这里也适用于haustoria和其他植物器官之间的比较。考虑到在连续体和过程植物形态学框架下该器官的结构，分子发育和功能，我建议将haustoria解释为形态失配。