360 On some American forms of Cham covonata. [May, 



or laxity of growth, seems to vary greatly from differences in the 

 character of the water, exposure, et cetera. The plant has been 

 thought to be free from incrustation, but one form from Canada 

 (Pacific Railway survey) is so completely incrusted that it is ex- 

 tremely brittle, and when dry has a gray color ; while another 

 form has a most peculiar zonular incrustation, giving the plant a 

 variegated appearance. 



The development of bracts seems to be most capricious ; though 

 the comparative length of bracts and sporangia seems to be 

 pretty constant in any one locality, the posterior development 

 varies in a single plant, and at times on a single leaf, one node 

 exhibiting verticillate bracts while the next node has absolutely 

 no bracts on its dorsal aspect : this we often find to be the case 

 in the longest bracted forms (var. Schweinitzii). 



In America we have every length of anterior bracts from two 

 to three times the length of the sporangium, a little longer, of 

 equal length, a little shorter, to very short bracts, one-half or 

 even a third its length. Some of the shortest bracted forms are 

 found with the largest sporangia and with verticillate bracts. 



Size of nucleus. — The smallest, mature nucleus we have yet 

 met with occurs in the form collected by Wright in New Mexico, 

 and determined by A. Braun as var. Braunii forma tenera ; it is 

 420 ft. long and has seven striae ; next in order is the Silver-city 

 form, recently found, 500 ft. with only five striae; one from Cali- 

 fornia is 500 ft. long with seven striae ; from Saranac lake, Ver- 

 mont, N. Carolina, etc., are forms 520 to 550 ft. long with longer 

 or shorter bracts; then come the more common long-bracted 

 forms (var. SckiveinitzU) with nucleus 550 to 650 ft. long with 

 8 to 9 striae ; then some forms with larger nucleus and very short 

 bracts, Penn. and Kansas, 660 to 780 (!) long with 9 to 10 striae. 

 Both the smallest and largest nuclei now known to us have been 

 associated with short bracts. 



The number of stria on the nucleus, representing the whorls ot 

 enveloping cells, varies considerably ; while in a general way they 

 are more numerous on the longest nuclei, yet a smaller nucleus 

 may have more than one somewhat larger ; the delicate Saranac 

 form has 9 striae, while the larger Vermont form has only 7 (the 

 same as the delicate Braunii- tenera) though the nucleus is larger. 

 The Silver-city form with a nucleus 500 ft. long has 5 striae, while 

 Braunii-tenera nucleus 420 ft. has 7 striae. 



