572 SUMMARY OF CURRENT RESEARCHES RELATING TO 



covering the tips of the cotyledons and surrounded by the perisperm. 

 The seed is raised by the elongating hypocotyl and clings to the tips 

 of the cotyledons till all the food is absorbed. The endosperm, which 

 is never more than one or two layers thick, never contaius any appre- 

 ciable amount of starch. In the ripe seed it is full of aleurone-grains 

 which gradually disappear as germination proceeds, the starch in the 

 perisperm disappearing at % the same time from the endosperm outwards. 

 It is suggested that the function of the endosperm is to digest the 

 starch stored in the perisperm, by the aid probably of a ferment pre- 

 pared from the proteid granules, and then to absoib and pass on the 

 digested material to the embryo. In Heckeria umbellata the process 

 is almost identical with that found in Peperomia. In Canna, Dianthus 

 and Cerastium, Polygonum and other cases, the thin layer of endosperm 

 about the cotyledons apparently serves the same purpose as in Peperomia. 

 The author believes that the sporophyte of the second generation is 

 nourished by that of the first generation always through the inter- 

 mediate gametophyte. 



Germination of Seeds of Carapa guianensis.* — J. W. Harshberger 

 has studied the germination of the seeds of this tropical forest tree 

 (natural order Meliaceae). The capsule is about the size and shape of 

 a coco-nut, and is filled with angular seeds, ten to twelve of which are 

 packed within the woody pericarp. Germination begins before the 

 seeds leave the capsule ; they are held in place by the interwoven mass 

 of secondary roots. The stem elongates some 4 to 6 in. and emerges 

 from the interior of the partially opened seed-vessel. The seeds lose 

 their vitality if allowed to remain for some time iu a dry place. They 

 are an inch to an inch and a half in diameter, with woody coats ; the 

 interior is tilled with the fleshy conferruminate cotyledons. The coty- 

 ledons contain no starch, the reserve material consisting of oil and 

 proteid bodies. In germination the hard coat cracks, the radicle first 

 protrudes and develops numerous secondary roots; the plumule follows. 

 The rapidly elongating stem bears at first closely appressed scale-leaves ; 

 after a time there arises a pair of opposite abruptly pinnate bijugate 

 leaves. Carapa guianensis, which is a land plant, differs from G. moluc- 

 censis, which is a mangrove plant, in not having the tuber-like radicle 

 and the pneumatodes which characterise the latter. 



Physiology. 

 Nutrition and Growth. 



Observations on Transpiration.f — C.C.Curtis describes the results 

 of numerous experiments on the apparently irregular variations in the 

 rate of transpiration. He finds that on dull days when the intensity 

 of the light is uniform or at least not in keeping with the time of day, 

 the transpiration curve shows a pronounced maximum near midday and 

 is also characterised by minor fluctuations which occur independently 

 of climatic changes. Illumination by an electric light of 900 candle- 

 power under uniform external conditions showed a periodicity in the 

 transpiration of several plants corresponding in the main with the curves 



* Froc. Acad. Nat. Sci. Philadelph., 1902, pp. 122-5. 

 t Full. Torr. Bot. Club, xxix. (1902) pp. 359-73. 





