,IZ PHANEROGAMS. 



olum, Trapa, Naiadeoe, Alismacese, Potamogetoneae, Orchideae ; in Canna even this 

 rudimentary production of endosperm appears to be suppressed. 



During the formation of the endosperm, the embryo-sac usually increases in 

 size, and thus displaces the tissue of the nucleus which still to a certain extent 

 surrounds it ; only in a few cases is the nucleus still partially or entirely preserved ; 

 it becomes filled with food-materials, like the endosperm, and replaces this latter 

 as a reservoir of reserve-materials for the embryo. In Scitamineae {e. g. Canna), 

 this tissue, the Perispcr??i, is very strongly developed, while the endosperm is alto- 

 gether wanting ; in Piperaceae and Nymphaeaceae there is a small endosperm in the 

 ripe seed, lying in a protuberance of the much larger perisperm. 



While the endosperm surrounded by the embryo-sac increases in size, the 

 Tes/a is formed from the development of the integuments which accompanies 

 that of the endosperm ; but in Criiium capense and some other Amaryllideae the 

 growing endosperm is stated by Hofmeister to burst the testa and even the wall 

 of the ovary; its cells produce chlorophyll, and the tissue remains succulent and 

 forms intercellular spaces (which does not occur in other cases). In Ricinus a 

 similar growth takes place when the ripe seed germinates in moist earth, bursting 

 the testa (according to von Mohl) ; and the endosperm, previously ovoid and from 

 8 to lomm. long, is transformed into a flat broad sac 20 to 25 mm. in length, which 

 surrounds the growing cotyledons until they have absorbed all the food-materials 

 from it. 



In Monocotyledons and many Dicotyledons the embryo remains small and 

 either enveloped by the endosperm or lying by its side (as in Grasses) ; its cells, 

 which are in close contact without intercellular spaces, become filled, until the seed 

 is ripe, with a protoplasmic substance and fatty matter or starch or both, in which 

 case they remain thin-walled; the endosperm then appears as the mealy (full of 

 starch) or fatty nucleus of the ripe seed, the embryo being found by its side or 

 within it ; but it is often horny in consequence of a considerable thickening of 

 its cell-walls which have the power of swelling {e.g. the date and other Palms, 

 Umbelliferse, Coffea, &c.) If this thickening has taken place to a very great extent, 

 the endosperm may fill up the testa as a hard mass, forming, for instance, the 

 ' vegetable ivory ' in the Phytelephas. In these cases the thickening-masses of the 

 endosperm-cells, which are absorbed during germination together with their proto- 

 plasmic and fatty contents, serve for the first nourishment of the embryo. The ripe 

 endosperm, when copiously developed, has usually the form of the entire ripe seed, 

 being uniformly covered by its testa ; its external form is therefore generally simple, 

 often round ; although considerable deviations from this frequently occur, especially 

 among Dicotyledons. Thus, for instance, the substance known as the 'coffee-berry' 

 consists, with the exception of the minute embryo w^hich is concealed in it, entirely 

 of the horny endosperm ; but this, as a transverse section shows, is a plate folded 

 inwards at its margins. The marbled (ruminated) endosperm which forms the 

 nucleus of the nutmeg (the seed of Myristica /ragrans), and the areca-nut (the 

 seed of the areca-palm), owes its appearance to the circumstance that an inner 

 ^dark layer of the testa grows in the form of radiating lamellae between narrow 

 fold-like protuberances of the light-coloured endosperm. The ripe endosperm is 

 either a perfectly solid mass of tissue, or it possesses an inner cavity, as in Sirychnos 



