硬序重寄生的形态学特征

硬序重寄生（檀香料）主要寄生在显脉松寄生（桑寄生科）上，是全寄生性的细小灌木，有许多特化的形态和结构特征；胚芽退化；胚根发育穿透寄主的树皮，进入寄主体内，形成寄生根。寄生根分化成“皮层根”和行吸收功能的吸器根。由皮层根产生根出条，形成寄主体外部分。 根出条基部是一小段营养体段，其以上是在成熟时占大部分的生根体段。茎上互生鳞片状叶，无或很少次生结构。单花具有很短的花梗，成熟时簇生于鳞叶腋内，单花被，通常4片花被片，花被下常有4个很小的小苞片，单性雌雄异株，4枚雄蕊，四室花药，下位子房一室，特立中央胎座。果实具果皮、果肉和一果核。果核外附一层含胶质的细胞，内含一粒种子。种子无种皮，胚乳发达；胚乳内有一柱状胚。

Morphological Features of Phacellaria rigidula Benth

Phacellaria rigidula Benth.(Santalaceae)is one kind of holo-parasitic mini-shrub.It parasites mainly on Taxillus calareas var. fargesii H.S.Kiu(Loranthaceae).It has many specialized morphological and ana tomical features.The plumule degenerated during the mature of the seed.The devel oping radicle penetrated bark of the host plant in which to form parasitic roots ,which differentiated further into cortical and haustorial root entering into va scular system.In fact,the parasitic plant out of the host is root sprout of the remind cortical root.For the plant there is only a very short vegetative section with very small alternate scale-leaves.The most part of the plant belongs to r eproductive section what bears flowers.The fascicled flowers do not have a commu nal rachis,but every flower has a very short pedicel with four little bracts.The flower is unisexual and dioecious with 4 tepals usually.The male one has 4 stam ens whose anthers are respectively of 4 locules.The female one has an inferior o vary made of 1 locule and free central placentation in which there are 4 ovules usually,but only one can develop to a seed.The fruit comprises of pericarp,sarco carp and drupe from outside.There is a layer of gelatinous cells from the carcar p on the drupe and one seed in the drupe.The seed has well developed endosperm w ith a columnar embryo in the central,but has not coat due to lacking of integume ntum.