ZOOLOGY AND BOTANY, MICROSCOPY, KTC. 667 



it appears in the ripe fruit exactly as it was in the pistil, but being 

 relatively much smaller is difficult to perceive. Iu the Perparieteae, it 

 sometimes occupies a more or less elevated position in the persistent 

 nucellus. By arresting the basal development of the albumen it protects 

 from destruction the region of the nucellus between itself and the 

 chalaza : this region is found in the ripe seed intercalated between the 

 tegument and the albumen, or the tegument and the embryo. Hence in 

 these cases there is a more or less voluminous perisperm. The author 

 insists on the necessity of looking for the hypostase and the perisperm 

 in future studies of pistil and ovule, and complains that M. Pechoutre 

 has, in the preceding memoir on the Kosacese, a member of the group 

 Perparieteae, completely ignored its existence. M. Van Tieghem asserts 

 that he has himself observed it in a good number of cases situated some- 

 times at the very base of the nucellus, sometimes higher up in its mass. 

 He gives as a special case the strawberry, in which the little woody 

 cupule can be seen immediately beneath the endosperm, and below it a 

 small disc of rudimentary perisperm. 



Development of Flower and Embryo of Spiraea.*— J. E. Webb has 

 studied the organogeny of the flower and the development of the embryo 

 mainly in Spireea japonica. He finds that the members develop in the 

 following order : — sepals, inner stamens, carpels, outer stamens, and 

 finally petals. The microsporangia are mature before the megasporangia. 

 In the former there is never any trace of archesporial cell or plate. 

 The peripheral layer of the hypodermal cells divides periclmally to form 

 two cell-layers, below which is a tapetal layer. The tapetum is merely 

 the outer layer of the sporogenous mass, and is distinguished from the 

 sporogenous cells merely by its position and nutritive function. The 

 author remarks that, although such an explanation of the tapetal layer 

 is impossible for many microsporangia, e.g. Cnicus, yet its possibility 

 has been suggested by Coulter in Banuncidus. By gradual changes 

 the tapetal is clearly differentiated from the spore-mother-cells, to form 

 a thick surrounding layer rich in food material. The inner of the two 

 layers between tapetum and epidermis is absorbed by the tapetum for 

 the benefit of the sporogenous tissue, and the tapetum itself becomes 

 ultimately disorganised and absorbed. The outer of the two layers 

 becomes the endothecium with large cells and thickened walls. In the 

 megasporangia, at a very early stage, several hypodermal cells at the 

 tip become enlarged, to form a mass of archesporial cells comparable 

 to that found in Rosa livida by Strasburger. By periclinal divisions a 

 hypodermal tapetal mass becomes separated from an inner sporogenous 

 mass. Successive periclinal divisions in the tapetum add much to the 

 length of the ovule and the distance from the sporogenous tissue to the 

 epidermis, and periclinal divisions in the latter also add to the length of 

 the ovule. Usually, one only of the megaspore-mothcr-cells enlarges 

 for division, but often two or three begin to divide and then all but one 

 break down. The successful megaspore is the one nearest the chalazal 

 end of the sac. It is very seldom that a megaspore nearer the micro- 

 pyle shows any signs of reaching maturity. The embryo-sac follows 

 the normal course of development, and at an early stage there occurs a 



* Bot. Gaz., xxxiii. (1902) pp. 451-60 (28 figs.). 



