EMBRYOGENY OF Pinus Pinaster. 57 



"^Attention may be drawn to certain points brought~^out by this 

 comparison : — 



(\.) Pollination takes place in the winter in this climate, elsewhere 



in the early svmimer. 

 (ii.) The ovule passes the late summer and autumn in the resting 

 condition here, but the same stage persists during the winter 

 : . ' elsewhere. 



(iii.) Pollination and fertilisation are separated by 14 to 15 



months here, but only by 12-13 months in England, etc. 

 (iv.) The Archegonia take longer to mature in this country, 

 being found for at least three weeks in the uninucleate 

 condition* as against one to two weeks elsewhere. 

 One other point seems worth recording, which is that only two 

 Archegonia are usually organised in the prothallus of this species, 

 whereas from three to five is reported as the normal number in 

 other Pines. Occasionally three are found in Pinus pinaster, but 

 very rarely more than that number. Probably at least 80 per cent, 

 of prothalli contain only two. ^^ 1 



In conclusion, I wish to express my thanks to Dr. H. H. W. 

 Pearson for the considerable trouble he took in collecting for me 

 some of the material used in 1907 on the Cape Flats at Kenilworth ; 

 that used in igo8 was collected in and around Cape Town. I wish 

 also to cordially thank Professor J. M. Coulter, of Chicago Univer- 

 sity, for very kindly sending me on loan certain back numbers of 

 the " Botanical Gazette," containing papers to which I had 

 occasion to refer. The microscopic investigation has been carried 

 out in the Botanical Laboratory of the South African College, Cape 

 Town. 



Summary. 



The embryo of Pinus penetrates the prothallus, in all probability, 

 not mechanically but by the secretion of an enzyme. 



The embryo grows for a time by means of a true apical cell, which 

 later becomes replaced by a group of apical meristematic cells. 



Karyokinetic activity is then transferred to the proximal end 

 of the embryo, and the first differentiation is between the root 

 periblem and the rest of the embryo, which later forms cotyledons, 

 stem apex and plerome. The cotyledons are all exactly equal and 

 equivalent in origin. 



Certain seasonal differences are noted in the life history of Pinus 

 in South-Western Cape Colony as compared with the Northern 

 Hemisphere. Only two Archegonia are usually formed in the 

 prothallus of Pinus pinaster. 



LITERATURE CITED. 



1. Blackman, V. H. {1898). On the Cytological features of 



fertilisation and related phenomena in Pinus sylvestris, 

 L.Phil. Trans. Roy. Soc, 190 : 395-426, pis. 12-14. 



2. Campbell, D. H. (1902). A University text-book of Botany. 



Macmillan & Co., London and New York. 1902. 



3. CoKER, W. C. (1902). Notes on the gametophytes and embryo 



of Podocarpus. Bot, Gaz. 33 : 89-107, pis. 5-7. 



* i.e. After the neck is cut off but before the central nucleus divide:-,. 



