1872 



A TEXTBOOK OF THEORETICAL BOTANY 



O 



Fig. 1779. — Floral diagram of 

 Primula. Priniulaceae. 



The inflorescence may consist of an umbel, a raceme, or a panicle, 

 though in many the flowers are solitary. 



The flowers (Fig. 1779) are usually regular, actinomorphic, hermaphro- 

 dite or occasionally unisexual by reduction. Many are heterostyled. 



The calyx is gamosepalous and persistent, 

 composed of five or sometimes four segments, 

 which are represented by points on the calyx 

 tube. 



The corolla is gamopetalous, regular, com- 

 posed of five or occasionally four petals, which 

 may be united basally into a tube but spread 

 out and separate above. In Glaiix the corolla 

 is absent, the sepals being coloured. The 

 androecium consists of five or more rarely 

 four stamens, which are arranged opposite the 

 petals, and are attached to them or to the base 

 of the corolla tube. The anthers are introrse 

 and dehisce longitudinally. 



The gynoecium is polycarpellary being 

 made up of five fused carpels, syncarpous, with a single simple style and 

 capitate stigma. The ovary is unilocular and superior. The ovules are 

 anatropous and numerous and the placentation is free-central. 



The fruit is a capsule, which may dehisce by five valves as in Primula, 

 or with circumscissile dehiscence, forming a pyxidium as in Anagallis. 

 The seed is endospermic but small in size and the embryo is straight. 

 Exceptions to the above description are found in certain species. Thus, 

 for example, the calyx may be composed of from five to nine sepals in 

 Trientalis, five or six in Lysimachia and four to five in Cefitunculus. The 

 flowers of the genus Con's are zygomorphic. 



The single whorl of stamens opposite the petals is interpreted as the 

 remnants of an earlier two-whorled condition, in which the outer whorl 

 has disappeared. This idea receives support from the fact that in Samohis 

 and in Soldanella, a whorl of scales is present opposite the sepals, which 

 may be the remnants of an outer stamen whorl. Anatomically the family 

 exhibits certainimportant features. Firstly there is the frequent development 

 of either simple or compound glandular hairs; secondly the common 

 occurrence of Casparian Bands on the radial walls of the endodermal cells 

 in the stem, and thirdly the absence of specialized cells around the stomata. 

 The family contains some twenty-five genera and about 550 species 

 which are very widely distributed though they are most common in north 

 temperate regions. 



The family is subdivided into the following tribes on the position of 

 the ovary, the aestivation of the corolla and the floral symmetry. 



I. Primuleae 



Ovary superior, capsule with valvate dehiscence, corolla lobes imbricated 

 in the bud. Primula, Androsace, Soldanella, Dodecatheon and Hottonia. 



