ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 197 



sperm-nuclei lie free in a common mass of cytoplasm and never form 

 distinct sperm-cells ; the two nuclei are unequal. The endosperm con- 

 tains about two thousand free nuclei before walls begin to be formed. 

 The archegonia appear about two weeks before fertilisation. He also 

 describes in considerable detail the independence of the male and female 

 chromatin during fertilisation. Eight nuclei are formed in the pro- 

 embryo at the base of the oosphere before the appearance of cell-walls. 



Comparative Embryology of the Cucurbitacese* — J. E. Kirkwood 

 U p ives the results of his work based on the study of sixteen genera of this 

 order, and relating chiefly to the development of the ovary and embryo- 

 sac. Some light is thrown on the systematic position of the family 

 which has been placed in recent Continental systems among the Sym- 

 petalae, owing chiefly to the union of the petals. The author of the 

 present memoir, however, finds that in all the sixteen genera certain 

 characters of Sympetala3 which have been regarded as fundamental 

 are contradicted. For instance, the ovule in the Sympetalae is con- 

 stantly characterised by a single very prominent integument, a much 

 reduced nucellus, and the elimination of tapetal tissue, the hypodermal 

 archesporial cell passing over directly into the mother-cell. But in all 

 the Cucnrbitaceae studied, the author finds the ovules with two integu- 

 ments, a well-developed nucellus, and often very extensive tapetal tissue. 

 The synergids are remarkable for their prominence and structure, and 

 the antipodals are ephemeral ; the endosperm is characterised by ex- 

 tensive growth and nutritive activity. 



Physiology. 

 Nutrition and Growth. 



Carbon Nutrition of Green Plants by Organic Substances.f — 

 J. Laurent gives a full account of his experiments on this subject. He 

 finds conclusive evidence of the value of carbohydrate foodstuffs to 

 green plants when presented to their roots. Thus maize roots were able 

 to make use of glucose solutions, the plants showing increase of dry 

 weight when grown in the dark ; and plants of various species, previously 

 deprived of starch, were able to manufacture starch in sunlight when 

 glucose, in 1-5 per cent, solutions, was presented to their roots, under 

 conditions which ensured absence of carbon dioxide. The author, how- 

 ever, failed to induce roots of green plants to digest starch, indicating a 

 fundamental difference between the nutrition of saprophytes, which have 

 this power, and autophytes. In a series of experiments on the influence 

 of organic substances on growth and form, the author found that growth 

 of the stem was checked in concentrated solutions. That this result does 

 not entirely depend on increased osmotic pressure is shown by the fact 

 that different results are obtained with solutions of equal concentration 

 of glucose and glycerin respectively. 



* Bull. New York Bot. Garden, iii. (1904) pp. 313-402 (12 pis.). See also J.M.C. 

 in Bot. Gazette, xxxix. (1905) p. 73. 



t Rev. Gen. Bot, xvi. (1904) pp. 14 -4s. 66-80,96 128, 155-66,188-202,231-42 



(7 pis.). 



