ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 265 



Reproductive. 



Embryo-sac and Embryo of Penstemon secundiflorus. — Arthur 

 Evans {Bot. Gaz., 1919, 67, 427-37, 1 pi.)- The author recapitulates 

 the results of previous work on o^enera of ScrophulariaceEe, and refers 

 to the fact that it was in members of this family that the development 

 of the embryo-sac and the embryo were first correctly studied, Hof- 

 meister in 1851 demonstrating in Lathraea, and Fedicularis that the 

 embryo was formed as the result of the fertilization of the egg, and not 

 from the end of the pollen-tube, as was believed by Schleiden and his 

 followers to be the case. The author finds that in this species the 

 embryo-sac is developed from a single megaspore. The antipodal cells 

 disorganize early ; the micropylar end becomes bulbous, while the 

 chalazal end becomes long and narrow, and is covered with a distinct 

 tapetum. The mature embryo-sac is found to be constantly gorged with 

 starch due to the non-utilization of the nutritive materials which pass 

 into the sac at a time of inactivity just before fertilization. Several 

 cases of double fertilization were observed. "Without resting after the 

 fusion with the sperm the endosperm nucleus divides, and free nuclei 

 migrate into the chalazal end of the sac where wall-formation begins. 

 The pro-embryo is pushed into this endosperm by an extreme growth of 

 the suspensor. The micropylar end of the sac disintegrates. Two 

 haustoria are formed, the micropylar by the growth of endosperm cells 

 from the chalazal end into the micropylar end, and the chalazal by a 

 growth of endosperm cells from the chalazal end out into the vascular 

 system. False polyembryony caused by fusion of two ovules seems to be 

 quite common in this species. A. B. R. 



Observations on the Morphology of Larix leptolepis. — ^ Joseph 

 Doyle {Scientific Proc. Royal Dublin Society, 15, 1918, 310-30, 2 pis.). 

 The author has studied the structure and development of the reproduc- 

 tive organs of this species — namely, the male and female strobilus 

 and gametophytes. There are very definite sacs in the microsporophyll 

 apex, especially in the bud ; these paired cavities are apparently homo- 

 logous with the paired canals of the vegetative leaf, and not with 

 abortive sporangia. The normal pollen-grain is large and without 

 wings ; the stalk and generative nucleus is already formed when it is 

 shed ; two marked cellulose walls bound the prothallial cells, and the 

 vestiges of a wall surrounds the generative nucleus. The development 

 of the grain is very similar to the irregular pollen-grain development in 

 Ficea canadensis. In wingless pollen and in the possession of marked 

 apical cavities in the microsporophyll, especially in the bud, Larix agrees 

 with Pseuclotsuga, and these two genera are in marked contrast to the 

 other genera of Abietineas. The author also deals with some points in 

 the anatomy of the female strobilus and gametophyte. There is a 

 gradual transition from basal vegetative leaves to cone-bracts, as in 

 Pseudotsuga, and the micropylar pollen-receiving device is similar to 

 what obtains in that genus. The female gametophyte develops as in 

 other Abietineas, but the megaspore membrane, very thick below, fades 

 over the top ; there are five long archegonia ; the neck-cells are in one 

 or two layers of four to eight cells. It is very similar to the female 



