808 SUMMARY OF CURRENT RESEARCHES RELATING TO 



situated at the base of the cavity, at about equal distances from the 

 chalaza and the micropyle. These disintegrated proembryonic cells 

 were taken by Hegelmaier for a special organ, peculiar to Lupinus, 

 formed before fertilization. In the species with two integuments this 

 phenomenon is not presented, owing to the permanent coherence of 

 the cells of which the suspensor is composed. 



Homology of the Ovule.* — F. Pax describes in detail instances of 

 phyllody of the carpels in Aquilegia vulgaris and formosa, with especial 

 reference to the genetic morphology of the ovule. He comes to the 

 same conclusion as Brongniart and Celakovsky,t that the two integu- 

 ments of the ovule together constitute a leaflet, on the upper side of 

 which the nucellus is equivalent to a metablast. The identity of this 

 leaflet with a pinnule of a fertile fern-frond is evident; and the 

 homologies of the parts may be expressed as follows : — 

 Fern. Ovule. 



Spore. 



Macrospore. Embryo-sac. 



Macrosporangium. Nucellus. 



Sorus. Several nucelli. 



Pinnule. Ovular leaflet. 



Reproductive Organs of Cycadese.J — An examination of the 

 reproductive organs of several species of Cycadese leads M. Treub to 

 the following general conclusions : — 



Each scale of the female cone (in Ceratozamia longifolid) bears two 

 sporangiferous lobes, each of which gives birth to a macrosporangium. 

 The macrosporangium can be detected in the interior of the lobe before 

 any external differentiation is perceptible. In each macrosporangium 

 can be recognized, at a later period, the three following parts : — 

 (1) the reproductive or primordial cells; (2) in the interior an 

 external parietal layer ; and (3) an internal compound parietal layer. 

 There is, in Ceratozamia, only a single macrospore mother-cell ; and 

 this does not divide, as in cryptogams ; it produces the single macro- 

 spore, in the same way as the embryo-sac is in general formed. 

 Shortly after the first appearance of the macrosporangium within the 

 sporangiferous lobe, this latter produces, on its apex, turned towards 

 the axis of the cone, two new formations, the nucellus and the integu- 

 ment. The nucellus owes its origin to one or two kypodermal layers 

 of the macrosporangium ; the integument is elevated on the lobe 

 around the nucellus. 



With regard to the homology of the parts — if Ceratozamia is to be 

 taken as a normal type of the Cycadese, as seems most probable — the 

 macrosporangium of Cycadeae, developed within the sporangiferous 

 lobe, is perfectly homologous to a sporangium of Ophioglossum ; the 

 nucellus and the integuments are new formations which find no 

 homologue in cryptogams. In the Cycadeas, therefore, neither the 

 nucellus nor the ovule represents a sporangium ; the sporangiferous 



* ' Flora,' Ixv. (1882) pp. 306-16 (1 pi.). 



t See this Journal, ante, p. 648. 



X Ann. Sci. Nat. (Bot.) xii. (1882) pp. 212-32 (7 pis.). 



