121 



Nitclla furnish common instances. They may be treated with 

 acetic acid and gentian-violet as described, in the latter case cut- 

 ting the long cells across and forcing out the contents with a 

 needle or fine forceps.* 



EXPLANATION OF FIGURES. 



(Plate CII.) 



Fig. I. — Filament of Nostoc X 350. 



2-6. — Cladophora (sp?) Showing process of cell-division followed in the 

 same cell. Fig. 2, draw^n at 9:30 a. m. Fig. 6, 2:05 r. m. x 300. 



7 — A much larger cell of the same X 175. 



S. — A dividing cell of Spirogyra (sp?) x 300. 



9- — A Desmid in process of division ; n. the nucleus ; p. pyrenoid, 



10-14. — Final divisions of the pollen-spores of Al/linn Canadcnsc, Acetic 

 acid, gentian violet X 350, In Fig. 10 the nuclear spindle in the left- 

 hand cell is seen from the pole. 



(Plate cm.) 

 Division of the pollen-spores of Podophylhtni pcltaium. All the figures were 



drawn from acetic acid, gentian violet preparations, and all but six are 

 magnified about 625 diameters, the latter about 1200. 

 Figs. 1-13. — Division stages of the primary nucleus of the mother-cell. Figs 



5-6 seen from the pole, the others from the side, 

 14-20. — Division of the secondarj' nuclei and formation of the spores, 

 21. — Two young isolated pollen-spores. 

 N-Nucleus; K-Nuclcar-plate ; F-Spindlc-fibcrs ; C-Cell-pIatc. 



On the Naming of "Forms," in the New Jersey Catalogue. 



In a recent number of the Bulletin, (Vol. xvi. 272) when 

 remarking on Mr. CockercFs paper on the naming of slight varie- 

 ties, I stated that I had introduced the term '' forma ** into the 

 Catalogue of Plants found in New Jersey, as a rank to include 

 physiological deviations or variations, such as color, odor and 

 si^e, reserving for the term " varietas " such as are manifestly 

 structural. I noted at that place that it was indeed difficult to 

 rigidly separate even these characters, so that very slight struc- 

 tural deviations in the size of organs or their number or amount 

 of division, might best come under the rank of ** forma/' I think 

 that it is only in the latter sense that the term has been used by 

 European authors, especially of the German school, and in their 

 microscopic habits of thought, attempts have been made to attach 



*See Strasburger-IIillhouse, p. 369 for Tradescanlia ; *' Eotanisches Practicum/' 

 ist edit. p. 516 for Cham and Nitclla. 



