and Laboratory Methods. 1859 



embryo-sac mother cell gives rise to four daughter cells, or potential macrospores, 

 and the greatest deviation when the embryo-sac mother cell is transformed 

 directly into a single macrospore, as in Liliiwi and other forms. The embryo- 

 sac mother cell — and also the pollen mother cell — is at once recognized by the 

 fact that at the first division of its nucleus the mitotic figure is heterotypic and 

 the reduced number of chromosomes appears. 



In the Cyperaceae a pollen mother cell gives rise to a single pollen grain, but 

 the mother cell in this case undergoes the customary divisions and one spore in 

 its development resorbs the other three. Asclepias has been reported as a case 

 in which a pollen mother cell gives rise to but a single microspore, just as the 

 embryo-sac mother cell in Liliicm gives rise to only one macrospore, but the 

 present paper shows definitely that each pollen mother cell gives rise to a row of 

 four microspores, each of which had been mistaken by former investigators for a 

 mother cell. The heterotypic mitotic figure and the reduction in tiie number of 

 chromosomes take place in the cell which gives rise to the row of four micro- 

 spores, thus identifying it as the mother cell. As the matter stands now, there 

 is no case of a pollen mother cell giving rise to a single microspore directly. 



Since the protoplasm of the pollen mother cell of Asclepias is particularly free 

 from granules, the writer made a thorough re-examination of the centrosome 

 problem, using the latest methods of botanists and zoologists, but was unable to 

 find centrosomes. While the waiter is not willing to assert that centrosomes will 

 never be demonstrated in the higher plants, he is nevertheless of the opinion 

 that they cannot be demonstrated by the methods now in vogue. c. j. c. 



CYTOLOGY, EMBRYOLOGY, 



AND 



MICROSCOPICAL METHODS. 



AGNES M. CLAYPOLE, Throop Polytechnic Institute. 



Separates of Papers and Books on Animal Biology should be sent for Review to Agnes M. Claypole, 



55 S. Marengo Avenue, Pasadena, Cal. 



k 



Deetjen. Untersuchungen ueber die Blutplatt- The author uses the following method 

 chen. Virchow's Arch. 164: 239-263, Tafl. to prevent the extremely thin blood- 

 '' '^° ■ film from drying before fixatives can be 



used : A drop of blood is spread on agar, not glass. The agar was prepared 

 by taking a one per cent, agar solution in which, after filtration, .0 per cent, sodium 

 chloride is dissolved; then .6 per cent, sodium metaphosphate and about .3 per 

 cent, di-sodium phosphate (K.HPO^). The metaphosphate alone preserves the 

 life of the blood plates. A drop of this solution is allowed to flow over the slide 

 and the agar cooled. Blood from the finger is spread on this cooled layer and 

 covered with a cover-glass. If this preparation is examined on a warmed stage 

 all the elements can be seen. The leucocytes move most actively in about five 

 minutes; usually at the same time, often earlier or later, the blood plates show 

 change of form. These structures put out amoeboid processes and move with 



