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PHANEROGAMS. 



The Ripe Seed depends, as respects its external nature, on the development of the 

 pericarp. The testa is in general thicker, firmer, and harder in proportion to the 

 softness of the pericarp, especially when this latter bursts to allow the dispersion of 

 the seeds. When, on the contrary, the pericarp is tough or woody, and encloses the 

 seeds until they germinate, as in the caryopsis, nut, drupe, and schizocarp, the testa 

 remains thin and soft, as also when the endosperm is strongly developed and very 

 hard and encloses a small embryo, as in the date and Phytelephas. The testa of 

 the seeds of dehiscent fruits is usually covered by a distinctly differentiated epi- 

 dermis ; and it depends on the configuration of this epidermis whether the seed has a 

 smooth appearance (as in the pea and bean), or displays a variety of sculpturing, such as 

 pits, warts, bands, and so forth (as in Hyoscyamus, Datura, Papaver, Nigella, &c.). The 

 epidermal cells of the seed not unfrequently grow into hairs ; cotton consists, for 

 example, of the long woolly hairs which clothe the seed of Gossypium ; in some cases 

 only a pencil-like tuft of long hairs is developed, as in Asclepias syriaca. The epidermal 

 cells of some seeds, as the flax, quince, Plantago Psyllium, arenaria, and Cynops, contain 

 layers of cellulose which have become converted into mucilage, swell up strongly with 

 water, become separated, and envelope the seeds when moist in a layer of mucilage. 

 Pericarps which are indehiscent and which contain small seeds not unfrequently assume 

 a character closely resembling that of the testa of the seeds of dehiscent fruits ; and 

 this is especially the case with the achenium and caryopsis, which are hence popularly 

 called seeds. The corona of hairs which serves as an apparatus for the dissemination of 

 many seeds through the air is frequently developed in the caryopsis as an appendage of 

 the pericarp (as the pappus of Compositae, which properly replaces the superior calyx). 

 The wings answering the same purpose which are formed during the development of 

 the testa of some seeds in dehiscent fruits (seen in an especially beautiful manner in 

 Bignonia) recur again on the pericarp of indehiscent fruits (as in Acer). The muci- 

 laginous epidermis spoken of above of the seeds of dehiscent fruits recurs in the epi- 

 dermis of the carcerulus of Salvia and other Labiatae, &c. These and a number of 

 other facts show that all that is essentially required in the development both of the 

 pericarp and the testa is to furnish means for the dissemination of the seeds in various 

 ways; structures which are morphologically very different thus attaining the same 

 physiological development, while those which are morphologically similar attain the 

 most various physiological development. A more detailed enumeration is therefore 

 more in the province of physiology and biology than of morphology and classification. 



To complete the subject of nomenclature, it only remains to remark that the part 

 of the seed where it has become detached from the funiculus— usually easily distin- 

 guished after falling out — is termed the Hilum or umbilicus. The micropyle is often 

 also to be recognized, lying, in anatropous and campylotropous seeds, close beside the 

 hilum (as in Faba, Phaseolus, and Corydalis), generally as a wart pitted in the middle. 

 When outgrowths occur on the seed, either along the raphe, as in Chelidomum majus, 

 Asarum, Viola, &c., or as a cushion covering the micropyle as in Euphorbia, they are 

 variously called Crest, Strophiole, or Caruncle. The Aril which envelopes the base of the 

 ripe seed or the entire seed as a fleshy succulent mantle and is easily removed from the 

 true firm testa, has already been described in detail. 



