420 MISS M. BENSON—CONTRIBUTIONS TO THE 
Relations of the Amentifere to Casuarina as revealed by Embryology. 
This part of my subject cannot be dealt with exhaustively until further and deeper 
researches have been made. Тһе agreement I have to point out is so mixed up with 
striking distinctions that we cannot, so far as our knowledge at present extends, in any way 
claim to have found a counterpart in our British Amentiferz to the extraordinary facts 
recorded by Treub for Caswarina. We know nothing of an embryo-sac without antipodals, 
for they are present and very conspicuous in the British Amentifers. In Betula, Alnus, 
and the Cupuliferze I have observed the fusing of the polar nuclei, and in every genus 
the presence of ѕупегоій and naked egg-cell. But Treub concludes his paper with the 
words :—'* A moins que de nouvelles recherches ne viennent nous apprendre le contraire, 
il faut considérer la famille des Casuarinées comme la seule de la classe des Chalazo- 
games." These new researches have now been made, and it will be no longer possible to 
classify the Casuarineze by themselves as Chalazogams. Alnus, Betula, Corylus, and 
Carpinus are also Chalazogams, and if we except the distinctions I have just pointed out 
in the early stages of the embryo-sac, almost all we have to record are, more or less, 
points of agreement. It will be convenient here to summarize the points of agreement 
between Casuarina and the British Amentiferz :— 
1. In the case of the Corylacee and Betulinez there is the prominent fact of their 
chalazogamy and all its concomitant adaptations. Among these I may mention the 
fusion of the tissue of the stylar region with the central strand, which is itself formed by 
the fusion of the two parietal placentæ, which have grown centripetally until they met 
and formed one strand, from the upper portion of which the now anatropous ovules spring 
(ср. figs. 39 and 40, also figs. 34 and 35, РІ. LXX.). 
Another special adaptation is the projection of the base of the nucellus into such a 
position that the pollen-tube, after travelling down the raphe in a course parallel with 
that of the vascular bundle, and following the trend of the cell-rows in the chalazal 
region, inevitably enters through the circular base of the nucellus (figs. 32, 34). We 
also see the sheath of crystals, which is so prominent a feature in Casuarina, although it 
would appear that our British Amentiferze have not specialized it to assist in the act of 
fertilization, as has occurred in Casuarina (figs. 34 and 35, also fig. 39). 
2. Тһе sporogenous tissue, already sufficiently described in another paragraph, although 
presenting striking points of difference in detail from that of Casuarina, constitutes, in 
the main, an important point of agreement. | 
3. The branching of the pollen-tube, especially the formation of recurved esca before 
its entry into the nucellus in the chalazogamic genera, and the resting stage that it passes 
through in the stylar tissue may, perhaps, be mentioned here. 
4. The prevalence of ceca formed by the embryo-sac is a remarkable feature of agree- 
ment. This character is so widely represented in the British Amentiferz that it may 
fairly be regarded as of taxonomic value. The fact that the tails of the sterile macro- 
spores in Casuarina serve for the unimpeded pathway of the pollen-tube up the nucellus, 
while that of Fagus is simply foraging for the needs of its embryo, only offers another 
example of the special adaptation to new functions of an organ already acquired by 
