ABSTRACTS OF FOUR LECTURES TO STUDENTS. 



521 



Cherry, would have an outer and an inner skin, with an intermediate 

 tissue. 



So would the ovary of a carpel. But when the two are adherent, the 

 inner skin of the tube and the outer skin of the carpel are arrested ; so, 

 then, the two "middle layers" are fused together, forming the fleshy 

 edible body of the Apple. The "core" represents the inner skin of the 

 ovary and contains the two pips or seeds, one on each margin of the 

 carpel.* The primary use or meaning of the tube is, as stated, to 

 secrete honey. In the Cherry the tube is lined with an orange-coloured 

 honey disc ; but when the tube is adherent to the ovary it is, of course, 

 only the rim which can supply it. This rim is also orange-coloured in 

 the Kose, but it appears to have lost its function in this genus, as bees 

 only come for pollen. 



In many flowers with adherent receptacular tubes, it is not the tube 

 but the top of the ovary which undertakes the office, as may be seen in 

 Elder, in which the exposed summit of the ovary and the base of the styles 

 are thickened, but in the Umbelliferce the top forms two cushion-like 

 structures between which the short styles rise. 



In some flowers the tube is prolonged far beyond the top of the ovary, 

 as may be seen in the Evening Primrose, Fuchsias, and Narcissus. 



In Apples and Pears the tube spreads out horizontally above the ovary, 

 forming a little dish, and so carrying the sepals, petals, and stamens to a 

 short distance from the styles which stand up in the middle. 



" Adhesion " is also used for the members of one whorl when they 

 adhere to one another. Thus whenever the petals "cohere," as of a 

 Primrose, the rule is that the stamens "adhere" to them. Heaths and 

 Canterbury Bells are exceptions. 



Any parts of a flower may secrete honey (though it is most commonly 

 done by the receptacle) by " glands," as in the Wallflower, which has two, 

 and in Geranium, which has five, or by a complete ring or disc, as is 

 characteristic of the Disciflorce. 



It is not very often that the sepals secrete it, but they form little 

 bowls full of honey in the Lime. The petals of many Ranunculaceous 

 plants are converted into honey-bearing " nectaries," as of Buttercup, 

 Aconite, and Larkspur. 



In some cases the stamens undertake the duty, as in Atragene, Pent- 

 stemon, and Chickweed. The carpels may also be honey-producers, either 

 at the base of the ovary or on the sides, as of the carpels of Marsh Mari- 

 gold, or the summit, as described above in Campanulas, Elder, and the 

 Umbelliferce. 



Begularity and Irregularity. — These terms are used in reference to 

 any whorl taken singly, to imply that all its parts are exactly alike or 

 " regular," or else one or more may differ from the other in size, shape, 



* It has been thought by some that such an " inferior " ovary, as it is called, is 

 entirely "axial," i.e. the receptacular tube with the exception of the summit or style- 

 bearing part (see Mudge and Maslen's Class Book of Botany, 1903, p. 288, fig. 153) ; 

 but a study of the distribution of the fibro-vascular cords which are supplied to the 

 carpels and ovules shows clearly that it is not so. I have illustrated the true arrange- 

 ments in my " Vascular System of Floral Organs," Journ. Linn. Soc, xxviii., pp. 159-60, 

 pi. xxviii., Ivy, &c. See also figures of other genera with inferior ovaries. In Alstrce- 

 meria, &c, the two included epidermides are sometimes partially incoherent and are 

 then distinguishable as epithelia. 



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