The term ‘sphaerocrystals’ (also sphaerites) in classic plant morphology was usually applied to spherical bodies visible in polarized light with a characteristic ‘Maltese cross’ and consisting of both inorganic and organic compounds. Initially sphaerocrystals were found in algal cells but were later also discovered in various organs of vascular plants (including seeds). Several authors noticed spherical particles on the seed surface and in testa cells of some Euphorbia species but a comprehensive study of this character in the genus (including the morphological origin of such particles) has not been carried out. We studied 72 species belonging to all 21 sections of Euphorbia subgenus Esula for presence of spherical particles on seed surface and in the testa using scanning, transmission, confocal laser electron microscopy, and light microscopy; histochemical and element analyses were also involved. We found that these particles have the same morphological features (including the demonstration of ‘Maltese cross’ in polarized light) as the ‘classic’ sphaerocrystals. We have recorded sphaerocrystals in 53 sampled species belonging to 20 sections of Euphorbia subgenus Esula; they are localized mostly in mesotesta cells and in some species are exuded onto the seed surface where they are often aggregated into clusters. Sphaerocrystals were absent in the sampled species (with one exception) of one of the major clades of the subgenus, formed by E. sect. Helioscopia and E. sect. Holophyllum. The absence of sphaerocrystals in this early divergent lineage of E. subgen. Esula may be related with adaptation of species of this lineage to more mesic habitats.

中文翻译：

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大戟亚属 Esula（大戟科）种子中的球晶：形态、发生及其与系统发育的关系

经典植物形态学中的术语“球晶”（也称为球晶）通常指在偏振光下可见的球形体，具有特征性的“马耳他十字”，由无机和有机化合物组成。最初在藻类细胞中发现了球晶，但后来也在维管植物的各种器官（包括种子）中发现了球晶。几位作者注意到一些大戟属物种的种子表面和种皮细胞中存在球形颗粒，但尚未对该属中的这一特征（包括此类颗粒的形态起源）进行全面研究。我们使用扫描、透射、共焦激光电子显微镜和光学显微镜研究了属于大戟亚属 Esula 全部 21 个部分的 72 个物种的种子表面和种皮中是否存在球形颗粒；还涉及组织化学和元素分析。我们发现这些粒子具有与“经典”球晶相同的形态特征（包括在偏振光下展示“马耳他十字”）。我们在属于大戟亚属 Esula 20 个科的 53 个样本物种中记录了球形晶体；它们主要集中在中种皮细胞中，在某些物种中，它们渗出到种子表面，在那里它们经常聚集成簇。该亚属主要分支之一（由 E. sect 形成）的采样物种（除一例外）中不存在球晶。 Helioscopia 和 E. sect。海棠属。 E. subgen 的早期分化谱系中不存在球晶。 Esula 可能与该谱系的物种对更湿润的栖息地的适应有关。