TRANSACTIONS OF SECTION K. 865 



naent of the antlierozoids in Zamia is unique. lu the generative cell two compara- 

 tively very large bodies are found accompanying the nucleus, which very greatly 

 resemble centrosomes, but which differ from any centrosomes that have been de- 

 scribed. The generative cell divides, forming two daughter-celLs, each of which forms 

 a motile antherozoid. In the prophases of the division the centrosome-like bodies in- 

 crease in size, becoming from 18 to 20 /x in diameter, an exterior wall becomes plainly 

 distinguishable, and the contents become vacuolate. During the formation of the 

 spindle, the kinoplasmic filaments centered upon the centrosom-like bodies entirely 

 disappear, apparently being utilised in forming the spindle. The spindle is inter- 

 nuclear, thefilamentshavingno visibleconnection withthe centrosome. In the monas- 

 ter stage of the division the outer membrane of the centrosome-like bodies has the ap- 

 pearance of breaking up into fragments, the contents contracting away from the 

 wall. During the formation of the cell-plate the outer membrane may be seen to have 

 broken, and the contents are then visible asa. small cluster of granules in the cytoplasm. 

 The membrane formed by the broken wall of the centrosome-like bodies becomes 

 extended in length, forming a band which moves outward and becomes appressed 

 against the Hautschicht of the antherozoid cell. This band grows in length, 

 finally forming from 5 to G turns around the cell, which are arranged in the form 

 of a helicoid spiral. While this band is still short, protuberances can be noticed 

 on its outer surface, which ultimately grow into the motile cilia of the mature 

 antherozoid. The antherozoids of Zamia are surprisingly large, being plainly 

 visible to the unaided eye. They are ovate or compressed, spherical in shape, and 

 from 258 to 332 /i in length by 258 to 306 fi in width. Their motion and de- 

 velopment were studied in 10 per cent, sugar solution, in which they could be kept 

 living and moving for over two hours. In fecundation from two to four anthero- 

 zoids enter each archegonium, only one of which takes part in fecundation. In 

 the actual process of fecundation, the nucleus only appears to take part, the 

 cytoplasm and cilia bearing band probably remaining in the cytoplasm of the 

 archegonium. The first division of the fecundated oosphere has not been observed. 

 In later divisions, however, which have been carefully studied no indication of 

 centrosomes could be found. The centrosome-like body in Zamia seems thus to be 

 a temporary organ of the cell, having the special and unique function of forming 

 the motile organs of the antherozoid. 



2. On Diagrams illustrating the result of Fifty Fears' Experimenting on 

 the Growth of Wheat at Rothamsted, England. By Dr. H. E. Arm- 

 strong, F.R.S. 



3. A Preliminary Account of a New Method of Investigating the Behaviour 

 of Stomata. By Francis Darwin, F.R.S. 



The method resembles in principle Stahl's cobalt test, inasmuch as it only 

 indirectly indicates the condition of the stomata. Both are, strictly speaking, 

 methods for localising the transpiration of leaves, and both, to some degree, 

 measure the amount of transpiration. The instrument made use of in the present 

 researches is a hygroscope depending for its action on the extreme sensitiveness to 

 watery vapour of certain substances. The best material consists of thin sheets of 

 horn treated in a special manner, and known as ' Chinese sensitive leaf.' The 

 other is what is used for the toys described as ' fortune-telling ladies,' ' magical 

 fish,' &c. AVhen either of these membranes is placed on a damp surface it 

 instantly curves with the concavity away from the source of moisture. If one end 

 of a strip of the material is fixed to the lower surface of a block of cork, and is 

 placed on the stomatal face of a leaf, it is clear that only the free end can rise. It 

 is on this principle that the hygroscope is constructed, the angle to which the 

 hygroscope tongue rises bemg a rough indication of the degree of transpiration. 

 Thus on a leaf having stomata only below, the index of the hygroscope remains at 

 aero on the upper surface of the leaf, while on the lower side it instantly rises to 



1897. 3 K 



