ZOOLOGY AND BOTANY, MICKOSCOPY, ETC. 1027 



character of systematic value observed in tlie study of the embryology 

 of the dandelion. On comparing the same rudimentary stages of a 

 large number of families, it was found that the character of superior 

 or inferior ovary was the first to manifest itself. In the case of an 

 inferior ovary, the protuberance which is to develope into the flower is 

 arrested in its axial development, grows into a collar (the nascent 

 floral envelopes) ; and there soon appears an external constriction 

 separating the floral envelopes above from the ovary below. In the 

 case of a superior ovary, the axial development is continued, and there 

 is no external constriction. On such a basis the Compositae stand at 

 the head of the list, then Umbeiliferfe, Eubiacese, &c. The second 

 group, that with a superior ovary, includes Leguminosae, Scrophu- 

 lariaceas, Labiatte, &c. 



Elasticity in the Fruit of Cactacese.* — Mr. T. Meehan remarks 

 on the elastic characters exhibited by the fruit of Mamillaria Heyderi 

 and other species. This Mamillaria, under cultivation, flowers in April 

 or May, and, after flowering, there is no sign of any development 

 in the fruit. The ovary is, indeed, buried between the closely 

 appressed walls of the bases of the mammae. Here the fruits, which 

 are two inches in length, remain undiscernible till just before the 

 next flowering season, when they suddenly emerge, and in a single 

 night apparently stretch out to their full length. The same sudden 

 appearance of the fruit has been noticed in Mamillai-ia Nuttalliana and 

 some allied Mexican species. That the sudden development is the 

 result of an elastic projection and not of a proper growth, is manifest 

 from the fact that the fruit is mature from its first appearance. 



Use of Spines iu Cactuses.f — Mr. T. Meehan considers that one of 

 the uses of these spines is to break the full force of the sun on the 

 plant. Plant-lovers set out their treasures in summer under " arbors " 

 of fish-netting or galvanized wii-e, and those who have no experience 

 would be surprised to find how the moving shadows of the twine or 

 wire lower the temperature. A mass of spines on a cactus must 

 certainly have the same effect. A cactus does not need much light on 

 its epidermis to keep it healthy. Mr. Meehan adds, " I do not suppose 

 I have yet reached the final purpose of spines in a cactus any more 

 than we have the final purpose in the existence of the cactus itself, 

 but that one use of cactus spines is to furnish a partial shade I feel to 

 be beyond a doubt." 



B. Physiology. J 



Theory of Descent.§ — Prof. E. Strasburger regards the act of re- 

 production in flowering plants as consisting in the union of the 



* Proc. Acad. Nat. Sci. Phikd., 1885, pp. 117-9. 



t Bull. Torrey Bot. Club, xii. (188o) pp. GO-1. 



I Tlii.s subdivifiion contains (1) Reproduction (including the formation of the 

 Embryo anf] acw^mpanyinf,' processes); (2) Germination; (3) Nutrition; (4) Growth; 

 (5) Respiration; {(}) Movement; and (7) Chemical processes (including Fermen- 

 tation). 



§ Strasburger, E., ' Neue Unters. iih. den Befructungsvorgang fiir eino 

 Theorie dor Zeugung,' Jena, 1884. See Naturforscher, xviii. (1885) p. 326. 



