55 



In the case of C. arenosa the cohimella is so much lengthened as to almost 

 touch the top of the incurved portion of the valves, and, if lengthened in course 

 of time so as to protrude be5'ond the dome so formed 

 by this incur\'ing, it would occupy a similar position to 

 the pistil of the angiosperms, and further, a develop- 

 ment of the free end (spur) of the sphorophyll would 

 produce a feature, calyx-like in character ; so that it is 

 possible we may be \-iewing here the prototype of a 

 capsule, say, identical with those of our Eucalypts, or 

 some other Myrtaceous genera. The sections given 

 under the origin of the cone valves certainly resemble 



,. c 1 r 7^ ; i^ " Xi j-1 Longitudinal section of Euca- 



a section of a capsule ot a hitcaivvtus species alter tne /v/,(,,s capsule after tertiiisa- 



^ ^ i J. jj^i^ j,j ovules. (Enlarged). 



fertilisation of the ovules, for Figures 32, 40, and ] 



41 illustrate a form of the central column almost 



approaching the above conditions, the columella being abnormally developed. 



XIV. ANGIOSPERMS v. GYMNOSPERMS. 



From the pre^aous account here given of the life history of the cone of 

 the Callitris, there are certain analogies one notices between corresponding 

 structures in the two large groups of the vegetable kingdom, i.e., the Angiosperms 

 and the Gymnosperms. 



In the case of the former division, the ovules are, as well known, completely 

 enclosed previous to fertilisation, and during the whole period of maturation 

 afterwards as seeds, whilst in the case of the latter division it is only in the pre- 

 fertile condition that the ovujes are gymnos. 



As soon as pollination is completed in Callitris, the thickening of the lower 

 portion of the sporophylls, as described above, takes place rapidly, and in a very 

 short space of time a closed cavit}^ is formed — a condition of things identical with 

 what is from the first in the Angiosperms, the ovary. The newly thickened 

 portions of the sporophylls now form the dome of this cavity, and the free ends 

 being throwTi back or spreading, resemble, as it were, or perhaps more correctly 

 speaking, correspond in this position to the sepals in Angiosperms ; in fact, one 

 might almost say that in the early stages of maturation, the thickened portions 

 of the sporophylls and their free ends are homologous respectively to the dome of 

 the ovary and the sepals in the Angiosperms. Here then, perhaps, are the proto- 

 types of the enclosed ovary, and the floral structure (sepals) of the x\ngiosperms. 



Then again, the period of maturation ha\dng been completed, a dehiscence 

 takes place similar to that of the Angiosperms. 



